1. |
- Bowallius, O., et al.
(author)
-
Evaluation of different oxidation methods for silicon for scanning capacitance microscopy
- 2001
-
In: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 4:03-jan, s. 81-84
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Journal article (peer-reviewed)abstract
- Different oxides, namely, native, thermal, and wet-chemical (H2SO4 + H2O2 based) oxides on Si are evaluated in the context of scanning capacitance microscopy (SCM). The samples investigated consisted of uniformly doped Si substrates and p-type epitaxial doping-staircase structures with concentrations ranging from 5 x 10(14) to 2 x 10(19) cm(-3) The bias for which the SCM signal (dC/dV) is maximised for the lowest doped region was used for comparing the different oxidation methods. It is shown that for a better evaluation of the surface oxide properties, it is essential to obtain dC/dV curves for a sufficiently large doping range. Best results in terms of low values of flat-band voltages (1 V), uniformity, and consistency across a large doping range were obtained for the wet-chemical oxide. For the native oxide case, the difference in the dC/dV peak bias Values obtained at regions doped to 5 x 10(14) to 10(17) cm(-3) was anomalously large and suggests appreciable distortion of the dC/dV curves. For the same oxidation procedure the full-width at half-maximum of the dC/dV curve obtained on the cleaved surface is typically 2 times larger than that on the planar (100) surface. It is most likely that interface states are responsible for the observed distortion.
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2. |
- Bowallius, O., et al.
(author)
-
Scanning capacitance microscopy investigations of SiC structures
- 2001
-
In: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 4:03-jan, s. 209-211
-
Journal article (peer-reviewed)abstract
- We have applied scanning capacitance microscopy (SCM) to investigate SIC structures grown by vapour-phase epitaxy. The SCM technique is evaluated using n- and p-type doping staircase structures with doping concentrations ranging from 10(16) to 10(20) cm(-3). The n- and p-type doping was obtained by doping SiC with nitrogen and aluminium, respectively. The sample cross-sections for SCM were obtained by simple cleaving. For doping levels above 10(17) cm(-3) the SCM data are consistent with doping data obtained independently from secondary ion mass spectroscopy (SIMS). Treating the samples with diluted hydrofluoric acid significantly improves the SCM signal for the low-doped regions. The SCM technique has been used to investigate doping redistribution in patterned regrowth of n- and p-type SIC around dry-etched mesas. In both cases, contrast variations were seen close to the mesa walls, indicative of doping variations; lower and higher incorporation for p- and n-type, respectively. The observations are shown to be consistent with the expected trends in dopant incorporation in the SiC material.
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3. |
- Duteil, F., et al.
(author)
-
Luminescence and microstructure of Er/O co-doped Si structures grown by MBE using Er and SiO evaporation
- 2000
-
In: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 3:5-6, s. 523-528
-
Journal article (peer-reviewed)abstract
- Er and O co-doped Si structures have been prepared using molecular-beam epitaxy (MBE) with fluxes of Er and O obtained from Er and silicon monoxide (SiO) evaporation in high-temperature cells. The incorporation of Er and O has been studied for concentrations of up to 2×1020 and 1×1021 cm-3, respectively. Surface segregation of Er can take place, but with O co-doping the segregation is suppressed and Er-doped layers without any indication of surface segregation can be prepared. Si1-xGex and Si1-yCy layers doped with Er/O during growth at different substrate temperatures show more defects than corresponding Si layers. Strong emission at 1.54µm associated with the intra-4f transition of Er3+ ions is observed in electroluminescence (EL) at room temperature in reverse-biased p-i-n-junctions. To optimize the EL intensity we have varied the Er/O ratio and the temperature during growth of the Er/O-doped layer. Using an Er-concentration of around 1×1020 cm-3 we find that Er/O ratios of 1:2 or 1:4 give higher intensity than 1:1 while the stability with respect to breakdown is reduced for the highest used O concentrations. For increasing growth temperatures in the range 400-575 °C there is an increase in the EL intensity. A positive effect of post-annealing on the photoluminescence intensity has also been observed.
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4. |
- Grivickas, P., et al.
(author)
-
Carrier lifetime investigation in 4H-SiC grown by CVD and sublimation epitaxy
- 2001
-
In: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 4:03-jan, s. 191-194, s. 191-194
-
Journal article (peer-reviewed)abstract
- Depth-resolved carrier lifetime measurements were performed in low-doped epitaxial layers of 4H silicon carbide samples. The technique used was a pump-and-probe technique where carriers are excited by an above-bandgap laser pulse and probed by free carrier absorption. Results from chemical vapour deposition samples show that lifetimes as high as 2 mus may be observed in the mid-region of 40 mum thick epilayers. For epilayers grown by the sublimation method decay transients were characterised by a fast (few nanoseconds) initial recombination, tentatively assigned to the 'true' lifetime, whereas a slow tail of several hundred microsecond decay time was assigned to trapping centres. From the saturation of this level at increased pumping we could derive the trapping concentration and their depth distribution peaking at the epilayer/substrate interface.
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5. |
- Jacob, AP, et al.
(author)
-
Ultrathin oxynitridation process through ion implantation in a poly Si1-xGex gate MOS capacitor
- 2003
-
In: Materials Science in Semiconductor Processing. - : Elsevier Science B.V., Amsterdam.. - 1369-8001 .- 1873-4081. ; 6:03-Jan, s. 37-41
-
Journal article (peer-reviewed)abstract
- Effect of temperature and time of heat treatment on the distribution of ion-implanted nitrogen in poly Si0.65Ge0.35 gate MOS samples was studied. Secondary ion mass spectrometry (SIMS) was used for the qualitative analysis of the nitrogen distribution. Rapid thermal processing was carried out for a temperature range of 950-1070degreesC for the redistribution of ions. The nitrogen implantation doses were 5 x 10(14) cm(-2), 2 x 10(15) cm(-2) and 5 x 10(15) cm(-2), all with an implantation energy of 50 keV. For a uniform distribution of nitrogen in the SiO2 region, an optimal temperature at a well calibrated time must be applied and this depends on the implantation dose. For medium and high concentrations the optimal conditions were 1050degreesC and 15s, and 1070degreesC and 15s, respectively. A uniform nitrogen distribution could be obtained throughout the SiO2 film. Prolonged heat treatment can cause degradation of the oxide layer and movement of the nitrogen and oxygen into the channel and the poly-Si0.65Ge0.35 layer.
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6. |
- Kuznetsov, A. Y., et al.
(author)
-
Self-interstitial migration during ion irradiation of boron delta-doped silicon
- 2000
-
In: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 3:4, s. 279-283
-
Journal article (peer-reviewed)abstract
- Boron delta layers in silicon, grown by molecular beam epitaxy and characterized by the secondary ion mass spectrometry, have been employed to investigate the migration of silicon self-interstitials during irradiation with MeV protons in the 500-850 degreesC temperature range. After growth, the samples were thinned from the backside to a thickness that made them transparent for the proton energies used. As a result, the generation rate of point defects can be considered as essentially uniform throughout the samples. However: the evolution of the boron profiles is almost identical to that observed after injection of self-interstitials caused by thermal oxidation of the samples at elevated temperature. This strongly indicates that the surface acts as a reflective boundary for the migrating self-interstitials or/ and an efficient sink for mobile vacancies. Furthermore, higher value of interstitial supersaturation in the near-surface region in proton-irradiated samples is consistent with experimentally detected depth dependence for immobile fraction in boron clusters. Then, activation energy of boron mobilization, (0.9 +/- 0.4) eV, was attributed to the dissociation of boron clusters.
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7. |
- Zetterling, Carl-Mikael, et al.
(author)
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UV-ozone precleaning and forming gas annealing applied to wet thermal oxidation of p-type silicon carbide
- 1999
-
In: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 2:1, s. 23-27
-
Journal article (peer-reviewed)abstract
- MOS capacitors using wet thermal oxidation of p-type 4H and 6H silicon carbide have been investigated using capacitance-voltage (CV) measurements. The interface state density was determined from displacements in the CV curves at room temperature after optical generation of carriers. Forming gas annealing at 400 °C after metallization was found to reduce the amount of deep interface states, and in combination with UV-ozone precleaning of the SiC substrates in a commercial system, the fixed oxide charge was also reduced.
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8. |
- Ahmad, Mohammed Metwally Gomaa, et al.
(author)
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Effect of precursor solutions on the structural and optical properties of sprayed NiO thin films
- 2017
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 64, s. 32-38
-
Journal article (peer-reviewed)abstract
- Nickel oxide thin films were deposited by a simple and low-cost spray pyrolysis technique using three different precursors: nickel nitrate, nickel chloride, and nickel acetate on corning glass substrates. X-ray diffraction show that the NiO films are polycrystalline and have a cubic crystal structure, although predominantly with a preferred 111-orientation in the growth direction and a random in-plane orientation. The deconvolution of the Ni 2p and O 1s core level X-ray photoelectron-spectra of nickel oxides produced by using different precursors indicates a shift of the binding energies. The sprayed NiO deposited from nickel nitrate has an optical transmittance in the range of 60-65% in the visible region. The optical band gap energies of the sprayed NiO films deposited from nickel nitrate, nickel chloride and nickel acetate are 3.5, 3.2 and 3.43 eV respectively. Also, the extinction coefficient and refractive index of NiO films have been calculated from transmittance and reflectance measurements. The average value of refractive index for sprayed films by nickel nitrate, nickel chloride and nickel acetate are 2.1, 1.6 and 1.85 respectively. It is revealed that the band gap and refractive index of NiO films by using nickel nitrate corresponds to the commonly reported values. We attribute the observed behavior in the optical band gap and optical constants as due to the change of the Ni/O ratio.
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9. |
- Ali Soomro, Razium, et al.
(author)
-
Development of sensitive non-enzymatic glucose sensor using complex nanostructures of cobalt oxide
- 2015
-
In: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 34, s. 373-381
-
Journal article (peer-reviewed)abstract
- The study reports the synthesis of cobalt oxide (Co3O4) nanostructures and their application in enzyme free electrochemical sensing of glucose. The synthesized nanostructures were elaborately characterized via number of analytical techniques including scanning electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The as-synthesized nanostructures of Co3O4 were found to exhibited nanodisc like morphology with the size dimension in range of 300-500 nm. The obtained morphological features were evaluated for their electrochemical potential towards oxidation of glucose which enabled development of sensitive (27.33 mu A mM(-1) cm(-2)), and stable enzyme free glucose sensor. In addition, the developed sensor showed excellent linearity (r(2)=0.9995), wide detection range (0.5-5.0 mM), lower detection limit (0.8 mu M) and extreme selectivity towards glucose in the presence of common interferents like dopamine (DP), ascorbic acid (AA) and uric acid (UA). The successfully application of developed sensor for real blood glucose analysis further reflects its capability for routine glucose measurement.
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10. |
- Alinejadian, Navid, et al.
(author)
-
Progress in additive manufacturing of MoS2-based structures for energy storage applications - A review
- 2022
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 139
-
Research review (peer-reviewed)abstract
- Investigation of next-generation manufacturing methods for the processing of functional materials and offering products with improved performance/functionalities has always been a challenge in terms of energy efficiency, cost-effectiveness, and eco-friendliness. Additive manufacturing (AM) attributes to rapid prototyping techniques that provide new opportunities to test new concepts and design complex 3D structures from metals, ceramics, and composites. Moreover, as a well-known transition metal dichalcogenide, Molybdenum disulfide (MoS2) is a two-dimensional (2D) material with outstanding electrochemical, physical, and mechanical properties that make it a potential candidate for energy storage electrodes via intercalation of different H+, Li+, Na+, and K+ cations. In this review, we discuss the existing conventional MoS2-processing methodologies and compare them with the novel additive manufacturing processes (especially laser-based powder bed fusion). The authors are convinced that the processing of prominent MoS2-based functional structures by the novel additive manufacturing processes can provide complex structures for different electrochemical applications, particularly for energy conversion/ storage systems.
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11. |
- Allal, Adel, et al.
(author)
-
A comparative theoretical investigation of optoelectronic and mechanical properties of KYS2 and KLaS2
- 2020
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 113
-
Journal article (peer-reviewed)abstract
- The ternary sulfides KYS2 and KLaS2 are two promising candidates for numerous applications, as much as white LED, X-ray phosphor and transparent conductor materials. However, theoretical studies on these materials are lacking, and many of their physical properties are still unknown. The aim of this work is to investigate the physical properties of the ternary sulfides KYS2 and KLaS2 namely, structural, elastic, optoelectronic, thermodynamic analysis, and set the substitution effect of Y and La elements in the two compounds. The fundamental properties calculations are based on ab-initio pseudopotential framework, with both local density approximation (LDA) and generalized gradient approximations (GGA) along with an expanded set of plane waves. The Becke, 3-parameter, Lee–Yang–Parr (B3LYP) hybrid functional is also employed to describe the electronic structures and optical properties. The optimized crystal parameters are correlated very well with the existing experimental data. The predicted values of the elastic constants demonstrate that the two compounds are mechanically stable and can be classified as brittle materials. The band structure analysis reveals that both KYS2 and KLaS2 have indirect band gap. The optical properties, like the refractive index, extinction, absorption and reflectivity coefficients, are determined for various polarizations of incident light, while both compounds present optical anisotropy. The obtained optical properties indicate the high transparency of KYS2 and KLaS2 in the infrared and visible regions, which makes them promising candidates for many of transparent applications. The thermodynamic properties are investigated with the help of quasiharmonic Debye model approximation. KYS2 has a larger bulk modulus value, which make it more beneficial in engineering applications. Calculations of thermodynamical properties indicate that KYS2 compound has better thermal conductivity, stronger chemical bonds and bigger hardness.
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12. |
- Allal, Adel, et al.
(author)
-
Phase stability, phonon, electronic, and optical properties of not-yet-synthesized CsScS2, CsYS2, and APmS(2) (A= Li, Na, K, Rb, Cs) materials : Insights from first-principles calculations
- 2022
-
In: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 150
-
Journal article (peer-reviewed)abstract
- Transparent conducting materials (TCMs) combine two exclusive properties, electrical conductivity and visible light transparency; which make them a unique class of materials. They are required in a wide range of applications in modern life ranging from touchscreen-based devices, flat panel displays, light-emitting diodes (LED), and solar cells. Most of the commercially and widely used TCMs are n-type, whereas the development of highperformance p-type TCMs remains an outstanding challenge in the actual time. Herein, using the newly developed SCAN meta-GGA and the hybrid HSE06 functionals, we have explored the structural stability and physical properties of not-yet-synthesized ternary materials CsScS2, CsYS2, and APmS(2) (A = Li, Na, K, Rb, Cs) to identify promising p-type TCMs. As result, the calculated formation energy, phase diagram and phonon dispersion curves confirm that these materials are thermodynamically stable and feasible to synthesize experimentally. All these materials, have large optical band gaps (larger than 3.4 eV), small hole effective masses (except for LiPmS2), and have no absorption and weak reflectivity of the visible light. Our work demonstrates that these compounds have suitable properties for p-type TCMs applications.
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13. |
- Ans, Muhammad, et al.
(author)
-
Spirobifluorene based small molecules as an alternative to traditional fullerene acceptors for organic solar cells
- 2019
-
In: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 94, s. 97-106
-
Journal article (peer-reviewed)abstract
- Four new three-dimensional (3D) acceptor-acceptor-donor (A-A-D) type of small molecule acceptors (Ml, M2, M3 and M4) were designed for better optoelectronic properties in organic solar cells. These molecules contain spirobifluorene as a 3D core unit, flanked with 2,1,3- benzothiadiazole (BT) units linked with the end-capped acceptor groups 2-(4-oxo-4,5-dihydrocyclopenta-b-thiophene-6-ylidene)malononitrile (M1), 2-(3-oxo-2,3-dihydro-1H-indene-1-indene-1-ylidene)malononitrile (M2), 2-(5,6-difluoro-3-oxo-2,3-dihydroindene-1-ylidene) malononitrile (M3) and 2-(5,6-dimethyl-3-oxo-2,3-dihydroindene-1-ylidene)malononitrile (M4). The optoelectronic properties of M1 -M4 were compared with the well-known reference molecule R, which has the same central BT-spirobifluorene-BT structure as Ml-M4 but is end-capped with the 2-(2-dicyanomethylene)-3-ethyl-4-oxo-thiazolidin-5-ylidenemethyl group. Among these molecules, M3 has the most appropriate frontier molecular orbital diagram for optoelectronic properties as deduced from MPW1PW91 calculations and also shows the maximum absorption peak at longest wavelength (569 nm) by TD-MPW1PW91 calculations with a polarizable continuum model for chloroform solution. These properties are due to the strong electron-withdrawing end-capped acceptor group which causes a red shift in the absorption spectrum. Computed reorganization energies indicate that the electron mobilities for M1-M4 are higher compared to that of reference R.
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14. |
- Balestra, F., et al.
(author)
-
NANOSIL network of excellence-silicon-based nanostructures and nanodevices for long-term nanoelectronics applications
- 2008
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 11:5-6, s. 148-159
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Journal article (peer-reviewed)abstract
- NANOSIL Network of Excellence [NANOSIL NoE web site < www.nanosil-noe.eu >], funded by the European Commission in the 7th Framework Programme (ICT-FP7, no 216171), aims at European scale integration of the excellent European research laboratories and their capabilities in order to strengthen scientific and technological excellence in the field of nanoelectronic materials and devices for terascale integrated circuits (ICs), and to disseminating the results in a wide scientific and industrial community. NANOSIL is exploring and assessing the science and technological aspects of nanodevices and operational regimes relevant to the n+4 technology node and beyond. It encompasses projects on nanoscale CMOS and beyond-CMOS. Innovative concepts, technologies and device architectures are proposed-with fabrication down to the finest features, and utilising a wide spectrum of advanced deposition and processing capabilities, extensive characterization and very rigorous device modeling. This work is carried out through a network of joint processing, characterization and modeling platforms. This critical interaction strengthens European integration in nanoelectronics and will speed up technological innovation for the nanoelectronics of the next two to three decades.
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15. |
- Bartosewicz, B., et al.
(author)
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Nanostructured GaN sensors for Surface Enhanced Raman Spectroscopy
- 2019
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 91, s. 97-101
-
Journal article (peer-reviewed)abstract
- The aim of this communication is to describe the range of applications of GaN-based platforms for trace detection and identification of biological and chemical agents using SERS technique. The methods of nano-structuring of GaN surface for SERS application are briefly described. The results of employing SERS method for analysis of Fentanyl and Bacillus Atrophaeus spores is demonstrated. The arguments are summarized which show the universal feature of GaN-based platforms as SERS sensor.
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16. |
- Bathen, Marianne Etzelmueller, et al.
(author)
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Dual configuration of shallow acceptor levels in 4H-SiC
- 2024
-
In: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 177
-
Journal article (peer-reviewed)abstract
- Acceptor dopants in 4H-SiC exhibit energy levels that are located deeper in the band gap than the thermal energy at room temperature (RT), resulting in incomplete ionization at RT. Therefore, a comprehensive understanding of the defect energetics and how the impurities are introduced into the material is imperative. Herein, we study impurity related defect levels in 4H-SiC epitaxial layers (epi-layers) grown by chemical vapor deposition (CVD) under various conditions using minority carrier transient spectroscopy (MCTS). We find two trap levels assigned to boron impurities, B and D, which are introduced to varying degrees depending on the growth conditions. A second acceptor level that was labeled X in the literature and attributed to impurity related defects is also observed. Importantly, both the B and X levels exhibit fine structure revealed by MCTS measurements. We attribute the fine structure to acceptor impurities at hexagonal and pseudo -cubic lattice sites in 4H-SiC, and tentatively assign the X peak to Al based on experimental findings and density functional theory calculations.
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17. |
- Carvahlo, A., et al.
(author)
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Studies of the VO centre in Ge using first principles cluster calculations
- 2006
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In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:4-5, s. 489-493
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Journal article (peer-reviewed)abstract
- The small or near-zero band gap of germanium found by supercell local density functional treatments causes difficulties in the study of the properties of charged defects in Ge. Here, we use large H-terminated Ge clusters together with a non-linear core corrected (NLCC) Ge pseudopotential to explore the structure, vibrational and electrical properties of the vacancy-oxygen complex (VO). The cluster possesses a gap sufficiently wide to contain defect related energy levels, thus allowing us to model the three charge states of the defect. The local vibrational modes (LVM) calculated for the neutral (VO0), negatively charged (VO-) and double negative (VO=) defect are 602, 684 and 694 cm- 1, and can be favourably compared with experimental values of 621, 669 and 716 cm- 1, respectively [Markevich VP, et al. Physica B 2003; 340-2, 844-8]. Using substitutional gold (Aus) as a marker defect, electric levels of VO are found at E (-/ 0) = Ev + 0.30 eV and E (= /-) = Ec - 0.29 eV, in excellent agreement with the respective experimental enthalpies for hole and electron emission Δ Hh (-/ 0) ≃ 0.32 eV and Δ He (= /-) = 0.26 eV, respectively. Finally, the migration, dissociation and reorientation energies of the defect are also reported.
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18. |
- Carvalho, A., et al.
(author)
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Density-functional theory study of Au, Ag and Cu defects in germanium
- 2008
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 11:5, s. 340-343
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Journal article (peer-reviewed)abstract
- Gold, silver and copper defects in germanium are modeled using density functional theory. The structures and electrical properties of the substitutional metals are calculated in excellent agreement with experiment. Interstitial Au, Ag and Cu are found to be shallow donors, in disagreement with a previous assignment of Cui to a hole trap in the lower half of the gap. Substitutional-interstitial metal (Mi - Ms) pairs and metal-vacancy pairs (Ms - V) are also investigated.
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19. |
- Christensen, J. S., et al.
(author)
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Phosphorus diffusion in the presence of threading dislocations in strain relaxed SiGe films
- 2006
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:4-5, s. 650-654
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Journal article (peer-reviewed)abstract
- We have studied phosphorus diffusion in strain relaxed Si1-xGex films (x = 0.1 and 0.2) by secondary ion mass spectrometry (SIMS). The relaxed films were grown with low-pressure chemical vapor deposition (LPCVD) on a Si substrate followed by a graded SiGe layer. Two sets of samples were prepared under different growth conditions, and by transmission electron microscopy (TEM) it was shown that these conditions resulted in one set of samples containing a high density of threading dislocations in the relaxed films, and one set with a low dislocation density. The SIMS profiles of the phosphorus distributions in the samples, after annealing in N-2-ambient in the temperature range of 700-950 degrees C, show that the phosphorus diffusion is significantly faster in the films with the high dislocation density. Furthermore, the data suggests that the fast diffusion is due to a higher mobility of the diffusing complex rather than an increase in the point defect concentration mediating the diffusion, a result which indicates that the threading dislocations may act as channels for the rapid dopant diffusion in SiGe.
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20. |
- Chulapakorn, Thawatchart, 1988-, et al.
(author)
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Luminescence of silicon nanoparticles from oxygen implanted silicon
- 2018
-
In: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 86, s. 18-22
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Journal article (peer-reviewed)abstract
- Oxygen with a kinetic energy of 20 keV is implanted in a silicon wafer (100) at different fluences, followed by post-implantation thermal annealing (PIA) performed at temperatures ranging from 1000 to 1200 degrees C, in order to form luminescent silicon nanoparticles (SiNPs) and also to reduce the damage induced by the implantation. As a result of this procedure, a surface SiOx layer (with 0 < x < 2) with embedded crystalline Si nanoparticles has been created. The samples yield similar luminescence in terms of peak wavelength, lifetime, and absorption as recorded from SiNPs obtained by the more conventional method of implanting silicon into silicon dioxide. The oxygen implantation profile is characterized by elastic recoil detection (ERD) technique to obtain the excess concentration of Si in a presumed SiO2 environment. The physical structure of the implanted Si wafer is examined by grazing incidence X-ray diffraction (GIXRD). Photoluminescence (PL) techniques, including PL spectroscopy, time-resolved PL (TRPL), and photoluminescence excitation (PLE) spectroscopy are carried out in order to identify the PL origin. The results show that luminescent SiNPs are formed in a Si sample implanted by oxygen with a fluence of 2 x 10(17) atoms cm(-2) and PIA at 1000 degrees C. These SiNPs have a broad size range of 6-24 nm, as evaluated from the GIXRD result. Samples implanted at a lower fluence and/or annealed at higher temperature show only weak defect-related PL. With further optimization of the SiNP luminescence, the method may offer a simple route for integration of luminescent Si in mainstream semiconductor fabrication.
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21. |
- Coutinho, J., et al.
(author)
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Ab initio modeling of defect levels in Ge clusters and supercells
- 2006
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:4-5, s. 477-483
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Journal article (peer-reviewed)abstract
- Most density-functional studies of defects in semiconductors invariably use (i) a supercell that imitates the host crystal, as well as (ii) a local treatment of the exchange-correlation potential. The first approximation has had an enormous success in many materials, provided that the size of cell is large enough to minimize long-range interactions between the infinite lattice of defects. For instance, these may arise from strain fields or from the overlap between shallow defect states. The second approximation, when combined with the periodic boundary conditions, leads to an essentially metallic density of states in Ge, which can compromise any investigation of electronic transitions involving gap levels. Here, we report on two approaches to surmount these difficulties, namely (i) to open the gap by reducing the host to a Ge cluster of atoms whose states are confined by a surface potential and (ii) to use supercells, but choosing carefully the Brillouin zone sampling scheme, taking k-points that minimize the admixture between defect-related gap states and the host density of states. These methods are utilized in the calculation of the electronic structure of the vacancy, divacancy, and vacancy-donor pairs in Ge
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22. |
- Ekström, Mattias, et al.
(author)
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Self-aligned contacts to ion implanted S/D regions in 4H-SiC
- 2023
-
In: Materials Science in Semiconductor Processing. - : Elsevier Ltd. - 1369-8001 .- 1873-4081. ; 168
-
Journal article (peer-reviewed)abstract
- The self-aligned silicide (salicide) process, where a metallic silicide is formed without lithographic definition to both source/drain-regions and the gate, is important for devices thanks to its ability to minimize parasitic resistances in scaled silicon CMOS technology. The challenge to transfer the process to SiC technology is two-fold: a single silicide has to give low resistance contacts to both ion implanted p-type and n-type simultaneously, and the typical temperatures required to form contacts to SiC is high enough that silicide agglomerates on polysilicon. In this work, we investigated if there exists a process window for salicide process for the purpose of developing a salicide process for SiC CMOS. Transfer length method structures were fabricated by ion implantation of phosphorus and aluminum to investigate simultaneous contacts to SiC. Bridge resistor structures (2μm width) were fabricated both with and without silicide-block to determine the silicide stability on highly in-situ doped polysilicon. The approach is design of experiment with multiple factors, including silicide composition, annealing temperature, deposited metal thickness and annealing time. The formation of self-aligned low resistive contacts to both n-type and p-type SiC was successful. The mutual process window for the co-existence of stable silicide on polysilicon and low resistive contacts to SiC, which is required for true salicide process, could not be found.
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23. |
- El Jamal, Ghada, et al.
(author)
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A scalable, resource-efficient process for synthesis of self-supporting germanium nanomembranes
- 2024
-
In: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 172
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Journal article (peer-reviewed)abstract
- The design of self-supporting membranes is gaining high interest in a broad range of applications, from nanodevices, optoelectronics, sensing, separation, and catalysis. In this report, we demonstrate a synthesis pathway for high quality ultrathin self-supporting germanium membranes using a highly scalable and resource-efficient process. We discuss the process flow, the compatibility between the materials and the processing chemicals, the important details for achieving the pure membranes and potential anomalies related to the etching process. Comprehensive characterization using SEM, EDX, TEM and nuclear microprobe analysis is employed for revealing the physical and structural properties of the synthesized membranes. The outcome of the fabrication process is large-area Ge nanomembranes with extremely flat and clean surfaces.
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24. |
- Gomeniuk, Y., et al.
(author)
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Low-temperature conductance measurements of surface states in HfO2-Si structures with different gate materials
- 2006
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:6, s. 980-984
-
Journal article (peer-reviewed)abstract
- Metal-oxide-semiconductor capacitors based on HfO2 gate stack with different metal and metal compound gates (Al, TiN, NiSi and NiAlN) are compared to study the effect of the gate electrode material on the trap density at the insulator-semiconductor interface. C-V and G-omega measurements were made in the frequency range from 1 kHz to 1 MHz in the temperature range 180-300 K. From the maximum of the plot G/omega vs. ln(omega) the density of interface states was calculated, and from its position on the frequency axis the trap cross-section was found. Reducing temperature makes it possible to decrease leakage current through the dielectric and to investigate the states located closer to the band edge. The structures under study were shown to contain significant interface trap densities located near the valence band edge (around 2 x 10(11) cm(-2)eV(-1) for Al and up to (3.5-5.5) x 10(12)cm(-2)eV(-1) for other gate materials). The peak in the surface state distribution is situated at 0.18 eV above the valence band edge for Al electrode. The capture cross-section is 5.8 x 10(-17)cm(2) at 200 K for Al-HfO2-Si structure.
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25. |
- Gottlob, H. D. B., et al.
(author)
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Investigation of high-K gate stacks with epitaxial Gd(2)O(3) and FUSINiSi metal gates down to CET=0.86 nm
- 2006
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:6, s. 904-908
-
Journal article (peer-reviewed)abstract
- Novel gate stacks with epitaxial gadoliniurn oxide (Gd(2)O(3)) high-k dielectrics and fully silicided (FUSI) nickel silicide (NiSi) gate electrodes are investigated. Ultra-low leakage current densities down to 10(-7) A cm(-2) are observed at a capacitance equivalent oxide thickness of CET = 1.8 nm. The influence of a titanium nitride (TiN) capping layer during silicidation is studied. Furthermore, films with an ultra-thin CET of 0.86 nm at a Gd(2)O(3) thickness of 3.1 nm yield current densities down to 0.5 A cm(-2) at V(g) = + 1 V. The extracted dielectric constant for these gate stacks ranges from k = 13 to 14. These results emphasize the potential of NiSi/Gd(2)O(3) gate stacks for future material-based scaling of CMOS technology.
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26. |
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27. |
- Haralson, Erik, et al.
(author)
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NiSi integration in a non-selective base SiGeCHBT process
- 2005
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 8:03-jan, s. 245-248
-
Journal article (peer-reviewed)abstract
- A self-aligned nickel silicide (salicide) process is integrated into a non-selective base SiGeC HBT process. The device features a unique, fully silicided base region that grows laterally under the emitter pedestal. This Ni(SiGe) formed in this base region was found to have a resistivity of 23-24 muOmega cm. A difference in the silicide thickness between the boron-doped SiGeC extrinsic base region and the in situ phosphorous-doped emitter region is observed and further analyzed and confirmed with a blanket wafer silicide study. The silicided device exhibited a current gain of 64 and HF device performance of 39 and 32 GHz for f(t) and f(MAX), respectively.
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28. |
- Hållstedt, Julius, et al.
(author)
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Incorporation of boron in SiGe(C) epitaxial layers grown by reduced pressure chemical vapor deposition
- 2005
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 8:03-jan, s. 97-101
-
Journal article (peer-reviewed)abstract
- In this paper the strain and electrical properties of epitaxial in situ B-doped (10(18)-10(21) cm(-3)) SiGeC layers (23, 28% Ge and 0, 0.5% C) has been investigated. The growth rate was shown to have a significant increase at 3 x 10(-2) mTorr diborane partial pressure. This point coincides with an enhancement in boron incorporation, which was explained by the strain compensation effect of boron in the highly strained SiGeC layers. In these samples, the total Ge and C content was shown to remain constant with increasing diborane partial pressure. The substitutional/active dopant concentration in SiGe layers was obtained by high-resolution X-ray diffraction by measuring the strain compensation effect of boron. The interaction between C and B in SiGe matrix was also investigated. This was compared with the active dopant concentration obtained from Hall measurements in order to achieve a Hall scattering factor of 0.3-0.7 for dopant concentrations between 3 x 10(18) and 5 x 10(21) cm(-3). The resistivity values of these layers were in the range 2 x 10(-2) -4 x 10(-4) Omega cm. Finally, it was shown that boron atoms in SiGeC layers locate preferably at substitutional sites in contrary to carbon atoms at both substitutional and interstitial sites.
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29. |
- Isheden, Christian, et al.
(author)
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pMOSFETs with recessed and selectively regrown Si1-xGex source/drain junctions
- 2005
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 8:1-3, s. 359-362
-
Journal article (peer-reviewed)abstract
- A new source/drain formation concept based on selective Si etching followed by selective regrowth of in situ B-doped Si(1-x)Ge(x)is presented. Both process steps are performed in the same reactor to preserve the gate oxide. Well-behaved transistors are demonstrated with a negligibly low gate-to-substrate leakage current.
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30. |
- Janke, C., et al.
(author)
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Ab initio investigation of phosphorus and boron diffusion in germanium
- 2008
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 11:5, s. 324-327
-
Journal article (peer-reviewed)abstract
- P and B diffusion has been modeled in Ge using ab initio methods along with the formation energies and electrical levels of various PV defects expected to be important in the deactivation of P in heavily n-doped Ge. The calculated activation barrier for B diffusion is found to be substantially lower than the measured barrier. However, the exceptionally large pre-exponential factor in the measured diffusivity points to a Meyer-Neldel rule operating and accounting for the discrepancy. The magnitude of the theoretical diffusivity is about a factor 10 lower than observed. For P diffusion, the experimental and theoretical results are in much closer agreement. The formation energy calculations show that all PV clusters are stable with respect to their component defects, and all but P V are predicted to introduce acceptor levels into the band gap. A simple analysis of possible formation mechanisms and Coulombic contributions suggests that as in Si, P V is the most important compensating center in heavily n-doped Ge.
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31. |
- Janke, C., et al.
(author)
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Supercell and cluster density functional calculations of the thermal stability of the divacancy in germanium
- 2006
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:4-5, s. 484-488
-
Journal article (peer-reviewed)abstract
- Large vacancy clusters, or voids, formed during growth have been reported in Ge. The divacancy is a precursor to such clusters, and is believed to be stable up to 150 or 180 {ring operator} C. It is also believed to form in Ge irradiated at room temperature where single vacancies are mobile. Density functional theory calculations have been performed to calculate the energy barriers for migration and dissociation of the divacancy. We find the binding energy in the neutral charge state to lie in the range 1.1-1.5 eV, and this increases for more negative charge states. The migration energies were found to vary from 1.0 to 1.3 eV from the singly positive to the doubly negative state
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32. |
- Jogi, Indrek, et al.
(author)
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Precursor-dependent structural and electrical characteristics of atomic layer deposited films : Case study on titanium oxide
- 2006
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:6, s. 1084-1089
-
Journal article (peer-reviewed)abstract
- Thin (10-20 nm) TiO2 films were atomic layer deposited from TiCl4, Ti(OC2H5)(4), H2O and H2O2 in the substrate temperature range 125-350 degrees C. The structure, chemical composition and electrical properties were correlated to the process temperature and nature of precursors, whereas the effect of precursors on conduction mechanisms was considerable only in the films grown at 125 degrees C, otherwise controlled by oxide-electrode interfaces. The use of chloride resulted in films with highest permittivity while the use of hydrogen peroxide resulted in lowest permittivity but also in lowest leakage. The post-deposition (pre-metallization) annealing resulted in densification and (re)crystallization of TiO2 layer but also in thickening of low-permittivity interface layers.
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33. |
- Kaushik, Priya Darshni, et al.
(author)
-
Modifications in structural, optical and electrical properties of epitaxial graphene on SiC due to 100 MeV silver ion irradiation
- 2018
-
In: Materials Science in Semiconductor Processing. - : Pergamon Press. - 1369-8001 .- 1873-4081. ; 74, s. 122-128
-
Journal article (peer-reviewed)abstract
- Epitaxial graphene (EG) on silicon carbide (SiC) is a combination of two robust materials that are excellent candidates for post silicon electronics. In this work, we systematically investigate structural changes in SiC substrate as well as graphene on SiC and explore the potential for controlled applications due to 100 MeV silver swift heavy ion (SHI) irradiation. Raman spectroscopy showed fluence dependent decrease in intensity of first and second order modes of SiC, along with decrease in Relative Raman Intensity upon ion irradiation. Similarly, Fourier-transform infrared (FTIR) showed fluence dependent decrease in Si-C bond intensity with presence of C = O, Si-O-Si, Si-Si and C-H bond showing introduction of vacancy, substitutional and sp(3) defects in both graphene and SiC. C1s spectra in XPS shows decrease in C = C graphitic peak and increase in interfacial layer following ion irradiation. Reduction in monolayer coverage of graphene after ion irradiation was observed by Scanning electron microscopy (SEM). Further, UV-Visible spectroscopy showed increase in absorbance of EG on SiC at increasing fluence. I-V characterization showed fluence dependent increase in resistance from 62.9 O in pristine sample to 480.1 Omega in sample irradiated at 6.6 x 10(12) ions/cm(2) fluence. The current study demonstrates how SHI irradiation can be used to tailor optoelectronic applicability of EG on SiC.
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34. |
- Khan, Muhammad Najam, et al.
(author)
-
Comparison of photocatalytic activity of zinc stannate particles and zinc stannate/zinc oxide composites for the removal of phenol from water, and a study on the effect of pH on photocatalytic efficiency
- 2015
-
In: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 36, s. 124-133
-
Journal article (peer-reviewed)abstract
- Zinc stannate and composite zinc stannate/zinc oxide particles were synthesized by a precipitation method in aqueous media at room temperature. As synthesized particles were characterized by SEM, TEM and XRD. Photocatalytic degradation of 50 ppm phenol in water in the presence of as synthesized particles was studied using the fluorescence decay. Experiments were carried out in both acidic and basic conditions to assess the stability of the catalyst particles and the role of pH on the photocatalytic degradation efficiency. Composite material showed enhanced activity in slightly acidic conditions. Efficiency of photodegradation was observed to be closely related to the isoelectric point of zinc stannate/zinc oxide composites.
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35. |
- Khirunenko, L.I., et al.
(author)
-
Complexes of self-interstitials with oxygen atoms in germanium
- 2008
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 11:5, s. 344-347
-
Journal article (peer-reviewed)abstract
- Interactions of germanium self-interstitials with interstitial oxygen atoms in Ge crystals have been studied by combining experimental and theoretical methods. Self-interstitials were created in oxygen-rich Ge crystals by irradiation with MeV electrons at 80 K, and I-O-related complexes were studied by means of infrared absorption spectroscopy, while the density functional theory was used to model structures, local vibrational modes and electronic properties of IO and I2O centers. It is argued that two absorption lines at 674 and 602 cm-1, which develop upon annealing of irradiated Ge:O crystals in the temperature range 180-220 K, are related to IO complexes, while another set of bands at 713 and 803 cm-1 is related to I2O. Those assignments are supported by the comparison with the calculated local vibrational modes of the defects.
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36. |
- Khosa, Rabia Y., et al.
(author)
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Electrical characterization of high k-dielectrics for 4H-SiC MIS devices
- 2019
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 98, s. 55-58
-
Journal article (peer-reviewed)abstract
- We report promising results regarding the possible use of AlN or Al 2 O 3 as a gate dielectric in 4H-SiC MISFETs. The crystalline AlN films are grown by hot wall metal organic chemical vapor deposition (MOCVD) at 1100 °C. The amorphous Al 2 O 3 films are grown by repeated deposition and subsequent low temperature (200 °C) oxidation of thin Al layers using a hot plate. Our investigation shows a very low density of interface traps at the AlN/4H-SiC and the Al 2 O 3 /4H-SiC interface estimated from capacitance-voltage (CV) analysis of MIS capacitors. Current-voltage (IV) analysis shows that the breakdown electric field across the AlN or Al 2 O 3 is ∼ 3 MV/cm or ∼ 5 MV/cm respectively. By depositing an additional SiO 2 layer by plasma enhanced chemical vapor deposition at 300 °C on top of the AlN or Al 2 O 3 layers, it is possible to increase the breakdown voltage of the MIS capacitors significantly without having pronounced impact on the quality of the AlN/SiC or Al 2 O 3 /SiC interfaces.
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37. |
- Khranovskyy, Volodymyr, et al.
(author)
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Temperature dependent study of basal plane stacking faults in Ag:ZnO nanorods by Raman and photoluminescence spectroscopy
- 2017
-
In: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 69, s. 62-67
-
Journal article (peer-reviewed)abstract
- We report the specific features of basal plane stacking faults (BSFs) in ZnO nanorods (NRs), studied by temperature dependent photoluminescence and Raman spectroscopy. At low temperature (4 K) the intense band of emission at 3.321 eV is attributed to the presence of BSFs defects and Ag as an acceptor dopant in ZnO. This specific peak red-shifts with the temperature increase, occupying the position 3.210 eV at RT. The nature of the emission is explained as exciton recombination of the electrons, confined in the homo-heterojunction QW, with the holes, localized near the Ag atoms close to SFs. Raman spectroscopy revealed that Ag: ZnO nanorods have slightly downshifted positions of the modes 330 cm(-1) and 440 cm(-1) by 4 cm(-1), which we explain as due to the presence of BSFs. It was also observed, that the longitudinal optical phonon mode ALO, which is common polar mode for ZnO, was not detected by Raman spectroscopy in the samples with high BSFs density. This feature can be explained as due to existence of the bound charge induced by the BSFs in the NRs.
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38. |
- Li, Zhicheng, et al.
(author)
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Direct observation of electron-beam-induced nucleation and growth in amorphous GaAs
- 2004
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 7:1-2, s. 19-25
-
Journal article (peer-reviewed)abstract
- In situ observation of the nucleation and growth stimulated by an electron beam in amorphous GaAs was performed using a high-resolution electron microscopy. The results showed that the crystallization was closely related to the current density of the electron beam. Crystallization could not take place when the current density was 50 pA/cm(2), nanocrystals with the random orientation formed under the 74 pA/cm(2) electron beam, large grains and twining structure formed during the crystallization induced by the 93 pA/cm(2) electron beam. Ionization process and electron-beam heating were suggested to be the possible mechanisms for the irradiation-induced crystallization.
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39. |
- Lin, Li, et al.
(author)
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An adhesive bonding approach by hydrogen silsesquioxane for silicon carbide-based LED applications
- 2019
-
In: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 91
-
Journal article (peer-reviewed)abstract
- We report an adhesive bonding approach using hydrogen silsesquioxane (HSQ) for silicon carbide (SiC) samples. A hybrid light-emitting diode (LED) was successfully fabricated through bonding a near-ultraviolet (NUV) LED grown on a commercial 4H-SiC substrate to a free-standing boron-nitrogen co-doped fluorescent-SiC epi-layer. The bonding quality and the electrical performance of the hybrid LED device were characterized. Neither voids nor defects were observed which indicates a good bonding quality of the proposed HSQ approach. A strong warm white emission was successfully obtained from the hybrid LED through an electric current injection of 30 mA.
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40. |
- Lo, Yi-Ling, et al.
(author)
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Determination of effective Ga/N ratio to control GaN growth behavior in liquid-target reactive magnetron sputter epitaxy
- 2024
-
In: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 176
-
Journal article (peer-reviewed)abstract
- The optimization of magnetron sputter epitaxy (MSE) for the high -volume production of high -quality GaN films is increasingly important. This study concerns the influence of key MSE process parameters - including the partial pressure of process gas, target -to -substrate distance (TSD), and growth temperature (TG) - for the synthesis of GaN thin films using a liquid Ga target. It is observed that the effective Ga/N ratio on the substrate surface determines the film's growth behavior and affects material's composition and luminescence properties. A lower Ar/N2 partial pressure ratio substantially enhances the crystalline quality, evidenced by the reduction in peak width of x-ray rocking curves from approximately 1.25 degrees (N -rich regime) to 0.35 degrees (Ga-rich regime) and improved GaN bandgap emission. While target sputtered in a highly Ga-rich condition significantly reduces the GaN growth rate (R), primarily due to Ga desorption in nitrogen -limited condition at elevated TG. Ion mass spectrometry and rate monitor measurements demonstrate that the Ga/N ratio can be controlled by adjusting Ar/N2 pressure ratio in MSE process. A reduction in TSD from 9.3 cm to 7 cm resulted in an increased R from 541 nm/h to 731 nm/h, corroborated by Simulation of Metal Transport (SIMTRA) analysis. Temperature -dependent studies revealed that films grown above 900 degrees C exhibited flat surface with high crystalline quality.
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41. |
- Monemar, Bo, 1942-, et al.
(author)
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Optical signatures of dopants in GaN
- 2006
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:1-3, s. 168-174
-
Journal article (peer-reviewed)abstract
- The characteristic optical spectra for shallow donors and acceptors in GaN are discussed. The most accurate photoluminescence (PL) data are obtained from samples grown on freestanding GaN substrates, where strain shifts are absent and a low spectroscopic line width is obtained. Recent PL data for excitons bound to the O and Si donors are discussed in some detail, giving accurate values for the binding energies and excited bound donor states. The Mg-acceptor is the most important one for p-doping, but the related optical spectra are controversial. We show that there are two acceptors present in Mg-doped GaN, with two different acceptor bound exciton peaks, and also two corresponding lower energy donor-acceptor pair spectra. We give tentative evidence for their interpretation. © 2006 Elsevier Ltd. All rights reserved.
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42. |
- Muhammad, Junaid, et al.
(author)
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Liquid-target Reactive Magnetron Sputter Epitaxy of High Quality GaN(0001ɸ)ɸ Nanorods on Si(111)
- 2015
-
In: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 39, s. 702-710
-
Journal article (peer-reviewed)abstract
- Direct current magnetron sputter epitaxy with a liquid Ga sputtering target hasbeen used to grow single-crystal GaN(0001) nanorods directly on Si(111)substrates at different working pressures ranging from 5 to 20 mTorr of pure N2,.The as-grown GaN nanorods exhibit very good crystal quality from bottom to topwithout stacking faults, as determined by transmission electron microscopy. Thecrystal quality is found to increase with increasing working pressure. X-raydiffraction results show that all the rods are highly (0001)-oriented. Thenanorods exhibit an N-polarity, as determined by convergent beam electrondiffraction methods. Sharp and well-resolved 4 K photoluminescence peaks at ~3.474 eV with a FWHM ranging from 1.7 meV to 35 meV are attributed to theintrinsic GaN band edge emission and corroborate the superior structuralproperties of the material. Texture measurements reveal that the rods haverandom in-plane orientation when grown on Si(111) with native oxide, while theyhave an in-plane epitaxial relationship of GaN[110] // Si[110] when grown onsubstrates without surface oxide.
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43. |
- Mustafa, Ghulam M., et al.
(author)
-
Study of optoelectronic and transport properties of MgLu2Z4 (Z=S, Se) spinels for optoelectronic and energy harvesting applications
- 2021
-
In: Materials Science in Semiconductor Processing. - : Elsevier. - 1369-8001 .- 1873-4081. ; 121
-
Journal article (peer-reviewed)abstract
- Intense research has been done to build materials that are potential candidates for energy storage applications. Spinels are of great interest in this respect because they have vast potential to be used in Mg-based batteries. To explore their energy storage as well as transport response, we calculate Mg-based spinels, namely MgLu2Z4 (ZS, Se). The full potential linearized augmented plane wave method has been used to examine their optoelectronic and transport response. An increase in the lattice constant has been observed by replacing S with Se, and our calculated values are in good agreement with those obtained experimentally. The Tran-Blaha modified Becke-Johnson exchange potential (TB-mBJ), has been used to study the optoelectronic and thermoelectric characteristics of the respective spinels. The dependence of these properties on the bandgap has also been observed. Replacing S with Se resulted in the transformation of the electronic bandgap from near-infrared to the visible region (MgLu2S4: 2.60 eV and MgLu2Se4: 2.00 eV). These results showed that these materials have the potential to be used in optoelectronic devices. The optical properties are discussed as a function of energy. Besides, the thermal transports are discussed with the help of Seebeck coefficient and figure of merit as a function of chemical potential and temperature.
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44. |
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45. |
- Pinto, H.M., et al.
(author)
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Formation energy and migration barrier of a Ge vacancy from ab initio studies
- 2006
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:4-5, s. 498-502
-
Journal article (peer-reviewed)abstract
- Here we present local density functional calculations of the formation and migration energies of a vacancy in large Ge supercells and hydrogen-terminated Ge clusters. Migration barriers for neutral (V0), negatively charged (V-) and double negatively charged (V=) vacancies were calculated by using symmetry-constrained atomic relaxations, as well as a nudged elastic band scheme. The formation energy of the neutral vacancy is estimated at 2.6 eV, whereas 0.4, 0.1 and 0.04 eV are obtained for migration barriers of V0, V- and V=, respectively. These figures account well for the formation kinetics of vacancy-impurity complexes in Ge at cryogenic temperatures, and are also in line with measured self-diffusion activation barriers obtained at elevated temperatures
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46. |
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47. |
- Shtepliuk, Ivan, et al.
(author)
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Raman probing of hydrogen-intercalated graphene on Si-face 4H-SiC
- 2019
-
In: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 96, s. 145-152
-
Journal article (peer-reviewed)abstract
- We report the results of in-depth Raman study of quasi-free-standing monolayer graphene on the (0001) Si- face of 4H-SiC, which contains similar to 0.1-2.10(11) cm(-2) sp(3) defects that have been introduced by hydrogen intercalation. The nature of the intercalation-induced defects is elucidated and ascribed to the formation of the C-H bonds. At the higher intercalation temperature in the formed monolayer graphene the defect-related Raman scattering displays a great enhancement and new spectral features attributed to D and D+D modes appear. Comprehensive statistical analysis of the Raman data enabled us to estimate the homogeneity of the Raman scattering processes and to separate strain and doping effects. Analysis of the compressive strain and carrier density maps revealed that the intercalation temperature of 900 degrees C and intercalation time of 1 h are more favorable conditions for conversion of the buffer layer to uniformly relaxed and p-doped monolayer graphene in comparison to annealing at 1100 degrees C for 30 min.
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48. |
- Siddiqui, Amna, et al.
(author)
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Carrier removal rates in 4H–SiC power diodes : A predictive analytical model
- 2023
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 167
-
Journal article (peer-reviewed)abstract
- An analytical model for predicting the proton and neutron radiation-induced carrier removal in silicon carbide (4H–SiC) diodes, is developed. It is primarily aimed towards a fast calculation of the carrier removal rates (ηe) and critical fluence (above which the diode drift layer is fully compensated), for a wide range of particle energies and diode ratings. The model utilizes the NIEL (non-ionizing energy loss) concept along with the actual carrier removal rate values for SiC available in the literature. A comparison to Si power devices is also made. The results from the predictive model suggest that diodes with a lower voltage rating can sustain a higher particle fluence and displacement damage before their drift layers are fully compensated. This provides radiation hardening guidelines for 4H–SiC power diodes at a device engineering level, which can help improve the reliability of circuits in harsh environment applications, such as space. The model is validated through TCAD simulations incorporating the proton-induced defects, as well as experimentally by irradiating SiC diodes with 2 MeV protons. The extracted compensation levels are in good agreement with those predicted by the analytical model, validating its potential in predicting carrier removal rate of SiC diodes for radiation prone environments.
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49. |
- Tia, Kai, et al.
(author)
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Modelling the static on-state current voltage characteristics for a 10 kV 4H-SiC PiN diode
- 2020
-
In: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 115
-
Journal article (peer-reviewed)abstract
- A 10 kV 4H-SiC epitaxial PiN diode is fabricated and the measured static on-state current voltage characteristics are used to tune the physical models and parameters included in TCAD device simulations. From the measurements it is found that the on-state voltage drop decreases more than 0.5 V at a current density of 100 A/cm(2), as the temperature is raised from room temperature to 300 degrees C. The steep slope of the IV-curve is, furthermore, maintained at elevated temperatures in contrast to most silicon PiN structures, where the decrease in mobility at higher temperatures typically decreases the IV slope, resulting in an increased voltage drop. Physical device simulations, involving common models for bandgap, incomplete ionization, charge carrier lifetime and mobility, are systematically compared and optimized to obtain the best fit with measured data. The negative temperature dependence can be simulated with good precision although the fitting is very sensitive to the choice of mobility models and, in particular, the acceptor ionization energy.
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50. |
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