| 1. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 2. |
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| 3. |
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| 4. |
- Bravo, L, et al.
(författare)
-
- 2021
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swepub:Mat__t
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| 5. |
- Tabiri, S, et al.
(författare)
-
- 2021
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swepub:Mat__t
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| 6. |
- Booker, Ian Don, et al.
(författare)
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Oxidation-induced deep levels in n- and p-type 4H- and 6H-SiC and their influence on carrier lifetime
- 2016
-
Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 6:1, s. 1-15
-
Tidskriftsartikel (refereegranskat)abstract
- We present a complete analysis of the electron- and hole-capture and -emission processes of the deep levels ON1, ON2a, and ON2b in 4H-SiC and their 6H-SiC counterparts OS1a and OS1b through OS3a and OS3b, which are produced by lifetime enhancement oxidation or implantation and annealing techniques. The modeling is based on a simultaneous numerical fitting of multiple high-resolution capacitance deep-level transient spectroscopy spectra measured with different filling-pulse lengths in n- and p-type material. All defects are found to be double-donor-type positive-U two-level defects with very small hole-capture cross sections, making them recombination centers of low efficiency, in accordance with minority-carrier-lifetime measurements. Their behavior as trapping and weak recombination centers, their large concentrations resulting from the lifetime enhancement oxidations, and their high thermal stability, however, make it advisable to minimize their presence in active regions of devices, for example, the base layer of bipolar junction transistors.
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| 7. |
- Booker, Ian Don, et al.
(författare)
-
Oxidation induced ON1, ON2a/b defects in 4H-SiC characterized by DLTS
- 2014
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2. - : Trans Tech Publications. ; , s. 281-284
-
Konferensbidrag (refereegranskat)abstract
- The deep levels ON1 and ON2a/b introduced by oxidation into 4H-SiC are characterized via standard DLTS and via filling pulse dependent DLTS measurements. Separation of the closely spaced ON2a/b defect is achieved by using a higher resolution correlation function (Gaver-Stehfest 4) and apparent energy level, apparent electron capture cross section and filling pulse measurement derived capture cross sections are given.
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| 8. |
- Glasbey, JC, et al.
(författare)
-
- 2021
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swepub:Mat__t
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| 9. |
- Anderson, Christopher P., et al.
(författare)
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Electrical and optical control of single spins integrated in scalable semiconductor devices
- 2019
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 366:6470, s. 1225-
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Tidskriftsartikel (refereegranskat)abstract
- Spin defects in silicon carbide have the advantage of exceptional electron spin coherence combined with a near-infrared spin-photon interface, all in a material amenable to modern semiconductor fabrication. Leveraging these advantages, we integrated highly coherent single neutral divacancy spins in commercially available p-i-n structures and fabricated diodes to modulate the local electrical environment of the defects. These devices enable deterministic charge-state control and broad Stark-shift tuning exceeding 850 gigahertz. We show that charge depletion results in a narrowing of the optical linewidths by more than 50-fold, approaching the lifetime limit. These results demonstrate a method for mitigating the ubiquitous problem of spectral diffusion in solid-state emitters by engineering the electrical environment while using classical semiconductor devices to control scalable, spin-based quantum systems.
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| 10. |
- Anderson, Christopher P., et al.
(författare)
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Five-second coherence of a single spin with single-shot readout in silicon carbide
- 2022
-
Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:5
-
Tidskriftsartikel (refereegranskat)abstract
- An outstanding hurdle for defect spin qubits in silicon carbide (SiC) is single-shot readout, a deterministic measurement of the quantum state. Here, we demonstrate single-shot readout of single defects in SiC via spin-to-charge conversion, whereby the defects spin state is mapped onto a long-lived charge state. With this technique, we achieve over 80% readout fidelity without pre- or postselection, resulting in a high signal-to-noise ratio that enables us to measure long spin coherence times. Combined with pulsed dynamical decoupling sequences in an isotopically purified host material, we report single-spin T-2 > 5 seconds, over two orders of magnitude greater than previously reported in this system. The mapping of these coherent spin states onto single charges unlocks both single-shot readout for scalable quantum nodes and opportunities for electrical readout via integration with semiconductor devices.
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| 11. |
- Arslan, Engin, et al.
(författare)
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SiC Substrate Effects on Electron Transport in the Epitaxial Graphene Layer
- 2014
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Ingår i: ELECTRONIC MATERIALS LETTERS. - : Springer Science and Business Media. - 1738-8090 .- 2093-6788. ; 10:2, s. 387-391
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Tidskriftsartikel (refereegranskat)abstract
- Hall effect measurements on epitaxial graphene (EG) on SiC substrate have been carried out as a function of temperature. The mobility and concentration of electrons within the two-dimensional electron gas (2DEG) at the EG layers and within the underlying SiC substrate are readily separated and characterized by the simple parallel conduction extraction method (SPCEM). Two electron carriers are identified in the EG/SiC sample: one high-mobility carrier (3493 cm(2)/Vs at 300 K) and one low-mobility carrier (1115 cm(2)/Vs at 300 K). The high mobility carrier can be assigned to the graphene layers. The second carrier has been assigned to the SiC substrate.
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| 12. |
- Astner, Thomas, et al.
(författare)
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Vanadium in silicon carbide: telecom-ready spin centres with long relaxation lifetimes and hyperfine-resolved optical transitions
- 2024
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Ingår i: QUANTUM SCIENCE AND TECHNOLOGY. - : IOP Publishing Ltd. - 2058-9565. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Vanadium in silicon carbide (SiC) is emerging as an important candidate system for quantum technology due to its optical transitions in the telecom wavelength range. However, several key characteristics of this defect family including their spin relaxation lifetime (T1), charge state dynamics, and level structure are not fully understood. In this work, we determine the T1 of an ensemble of vanadium defects, demonstrating that it can be greatly enhanced at low temperature. We observe a large spin contrast exceeding 90% and long spin-relaxation times of up to 25 s at 100 mK, and of order 1 s at 1.3 K. These measurements are complemented by a characterization of the ensemble charge state dynamics. The stable electron spin furthermore enables high-resolution characterization of the systems' hyperfine level structure via two-photon magneto-spectroscopy. The acquired insights point towards high-performance spin-photon interfaces based on vanadium in SiC.
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| 13. |
- Ayedh, H. M., et al.
(författare)
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Controlling the carbon vacancy in 4H-SiC by thermal processing
- 2018
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Ingår i: ECS Transactions. - : Electrochemical Society Inc.. - 1938-6737 .- 1938-5862. ; , s. 91-97
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Konferensbidrag (refereegranskat)abstract
- The carbon vacancy (Vc) is perhaps the most prominent point defect in silicon carbide (SiC) and it is an efficient charge carrier lifetime killer in high-purity epitaxial layers of 4H-SÌC. The Vc concentration needs to be controlled and minimized for optimum materials and device performance, and an approach based on post-growth thermal processing under C-rich ambient conditions is presented. It utilizes thermodynamic equilibration and after heat treatment at 1500 °C for 1 h, the Vc concentration is shown to be reduced by a factor-25 relative to that in as-grown state-of-the-art epi-layers. Concurrently, a considerable enhancement of the carrier lifetime occurs throughout the whole of >40 urn thick epi-layers.
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| 14. |
- Babin, Charles, et al.
(författare)
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Fabrication and nanophotonic waveguide integration of silicon carbide colour centres with preserved spin-optical coherence
- 2022
-
Ingår i: Nature Materials. - : NATURE PORTFOLIO. - 1476-1122 .- 1476-4660. ; 21, s. 67-73
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Tidskriftsartikel (refereegranskat)abstract
- Colour centres are a promising quantum information platform, but coherence degradation after integration in nanostructures has hindered scalability. Here, the authors show that waveguide-integrated V-Si centres in SiC maintain spin-optical coherences, enabling nuclear high-fidelity spin qubit operations. Optically addressable spin defects in silicon carbide (SiC) are an emerging platform for quantum information processing compatible with nanofabrication processes and device control used by the semiconductor industry. System scalability towards large-scale quantum networks demands integration into nanophotonic structures with efficient spin-photon interfaces. However, degradation of the spin-optical coherence after integration in nanophotonic structures has hindered the potential of most colour centre platforms. Here, we demonstrate the implantation of silicon vacancy centres (V-Si) in SiC without deterioration of their intrinsic spin-optical properties. In particular, we show nearly lifetime-limited photon emission and high spin-coherence times for single defects implanted in bulk as well as in nanophotonic waveguides created by reactive ion etching. Furthermore, we take advantage of the high spin-optical coherences of V-Si centres in waveguides to demonstrate controlled operations on nearby nuclear spin qubits, which is a crucial step towards fault-tolerant quantum information distribution based on cavity quantum electrodynamics.
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| 15. |
- Bathen, M. E., et al.
(författare)
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Anisotropic and plane-selective migration of the carbon vacancy in SiC : Theory and experiment
- 2019
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 100:1
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the migration mechanism of the carbon vacancy (VC) in silicon carbide (SiC) using a combination of theoretical and experimental methodologies. The VC, commonly present even in state-of-the-art epitaxial SiC material, is known to be a carrier lifetime killer and therefore strongly detrimental to device performance. The desire for VC removal has prompted extensive investigations involving its stability and reactivity. Despite suggestions from theory that VC migrates exclusively on the C sublattice via vacancy-atom exchange, experimental support for such a picture is still unavailable. Moreover, the existence of two inequivalent locations for the vacancy in 4H-SiC [hexagonal, VC(h), and pseudocubic, VC(k)] and their consequences for VC migration have not been considered so far. The first part of the paper presents a theoretical study of VC migration in 3C- and 4H-SiC. We employ a combination of nudged elastic band (NEB) and dimer methods to identify the migration mechanisms, transition state geometries, and respective energy barriers for VC migration. In 3C-SiC, VC is found to migrate with an activation energy of EA=4.0 eV. In 4H-SiC, on the other hand, we anticipate that VC migration is both anisotropic and basal-plane selective. The consequence of these effects is a slower diffusivity along the axial direction, with a predicted activation energy of EA=4.2 eV, and a striking preference for basal migration within the h plane with a barrier of EA=3.7 eV, to the detriment of the k-basal plane. Both effects are rationalized in terms of coordination and bond angle changes near the transition state. In the second part, we provide experimental data that corroborates the above theoretical picture. Anisotropic migration of VC in 4H-SiC is demonstrated by deep level transient spectroscopy (DLTS) depth profiling of the Z1/2 electron trap in annealed samples that were subject to ion implantation. Activation energies of EA=(4.4±0.3) eV and EA=(3.6±0.3) eV were found for VC migration along the c and a directions, respectively, in excellent agreement with the analogous theoretical values. The corresponding prefactors of D0=0.54cm2/s and 0.017cm2/s are in line with a simple jump process, as expected for a primary vacancy point defect.
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| 16. |
- Bathen, Marianne Etzelmueller, et al.
(författare)
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Dual configuration of shallow acceptor levels in 4H-SiC
- 2024
-
Ingår i: Materials Science in Semiconductor Processing. - : ELSEVIER SCI LTD. - 1369-8001 .- 1873-4081. ; 177
-
Tidskriftsartikel (refereegranskat)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. |
- Bathen, M. E., et al.
(författare)
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Influence of carbon cap on self-diffusion in silicon carbide
- 2020
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Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 10:9, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Self-diffusion of carbon (12C and13C) and silicon (28Si and30Si) in 4H silicon carbide has been investigated by utilizing a structure containing an isotope purified 4H-28Si12C epitaxial layer grown on an n-type (0001) 4H-SiC substrate, and finally covered by a carbon capping layer (C-cap). The13C and30Si isotope profiles were monitored using secondary ion mass spectrometry (SIMS) following successive heat treatments performed at 2300–2450◦C in Ar atmosphere using an inductively heated furnace. The30Si profiles show little redistribution within the studied temperature range, with the extracted diffusion lengths for Si being within the error bar for surface roughening during annealing, as determined by profilometer measurements. On the other hand, a significant diffusion of13C was observed into the isotope purified layer from both the substrate and the C-cap. A diffusivity of D = 8.3 × 106 e−10.4/kBT cm2/s for13C was extracted, in contrast to previous findings that yielded lower both pre-factors and activation energies for C self-diffusion in SiC. The discrepancy between the present measurements and previous theoretical and experimental works is ascribed to the presence of the C-cap, which is responsible for continuous injection of C interstitials during annealing, and thereby suppressing the vacancy mediated diffusion.
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| 18. |
- Bergman, Peder, 1961-, et al.
(författare)
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Improved SiC Epitaxial Material for Bipolar Applications
- 2008
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Ingår i: Proc. of MRS Spring Meeting 2008. ; , s. D05-
-
Konferensbidrag (refereegranskat)abstract
- Epitaxial growth on Si-face nominally on-axis 4H-SiC substrates has been performed using horizontal Hot-wall chemical vapor deposition system. The formation of 3C inclusions is one of the main problem with growth on on-axis Si-face substrates. In situ surface preparation, starting growth parameters and growth temperature are found to play a vital role in the epilayer polytype stability. High quality epilayers with 100% 4H-SiC were obtained on full 2″ substrates. Different optical and structural techniques were used to characterize the material and to understand the growth mechanisms. It was found that the replication of the basal plane dislocation from the substrate into the epilayer can be eliminated through growth on on-axis substrates. Also, no other kind of structural defects were found in the grown epilayers. These layers have also been processed for simple PiN structures to observe any bipolar degradation. More than 70% of the diodes showed no forward voltage drift during 30 min operation at 100 A/cm2.
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| 19. |
- Bergman, Peder, et al.
(författare)
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Radial Variation of Measured Carrier Lifetimes in Epitaxial Layers Grown with Wafer Rotation
- 2012
-
Ingår i: Materials Science Forum Vols 717 - 720. - : Trans Tech Publications Inc.. ; , s. 289-292
-
Konferensbidrag (refereegranskat)abstract
- In this report we present homoepitaxial growth of 4H-SiC on the Si-face of nominally on-axis substrates with diameter up to 100 mm in a hot-wall chemical vapor deposition reactor. A comparatively low carrier lifetime has been observed in these layers. Also, local variations in carrier lifetime are different from standard off-cut epilayers. The properties of layers were studied with more focus on charge carrier lifetime and its correlation with starting growth conditions, inhomogeneous surface morphology and different growth mechanisms.
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| 20. |
- Bernardin, Evans, et al.
(författare)
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Development of an all-SiC neuronal interface device
- 2016
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Ingår i: MRS Advances. - : Cambridge University Press. - 2059-8521. ; 1:55, s. 3679-3684
-
Tidskriftsartikel (refereegranskat)abstract
- The intracortical neural interface (INI) is a key component of brain machine interfaces (BMI) which offer the possibility to restore functions lost by patients due to severe trauma to the central or peripheral nervous system. Unfortunately today’s neural electrodes suffer from a variety of design flaws, mainly the use of non-biocompatible materials based on Si or W with polymer coatings to mask the underlying material. Silicon carbide (SiC) is a semiconductor that has been proven to be highly biocompatible, and this chemically inert, physically robust material system may provide the longevity and reliability needed for the INI community. The design, fabrication, and preliminary testing of a prototype all-SiC planar microelectrode array based on 4H-SiC with an amorphous silicon carbide (a-SiC) insulator is described. The fabrication of the planar microelectrode was performed utilizing a series of conventional micromachining steps. Preliminary data is presented which shows a proof of concept for an all-SiC microelectrode device.
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| 21. |
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| 22. |
- Bernardin, Evans K., et al.
(författare)
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Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface
- 2018
-
Ingår i: Micromachines. - : MDPI. - 2072-666X. ; 9:8
-
Tidskriftsartikel (refereegranskat)abstract
- Intracortical neural interfaces (INI) have made impressive progress in recent years but still display questionable long-term reliability. Here, we report on the development and characterization of highly resilient monolithic silicon carbide (SiC) neural devices. SiC is a physically robust, biocompatible, and chemically inert semiconductor. The device support was micromachined from p-type SiC with conductors created from n-type SiC, simultaneously providing electrical isolation through the resulting p-n junction. Electrodes possessed geometric surface area (GSA) varying from 496 to 500 K m(2). Electrical characterization showed high-performance p-n diode behavior, with typical turn-on voltages of 2.3 V and reverse bias leakage below 1 nArms. Current leakage between adjacent electrodes was 7.5 nArms over a voltage range of -50 V to 50 V. The devices interacted electrochemically with a purely capacitive relationship at frequencies less than 10 kHz. Electrode impedance ranged from 675 +/- 130 k (GSA = 496 mu m(2)) to 46.5 +/- 4.80 k (GSA = 500 K mu m(2)). Since the all-SiC devices rely on the integration of only robust and highly compatible SiC material, they offer a promising solution to probe delamination and biological rejection associated with the use of multiple materials used in many current INI devices.
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| 23. |
- Booker, Ian Don, et al.
(författare)
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Carrier Lifetime Controlling Defects Z(1/2) and RB1 in Standard and Chlorinated Chemistry Grown 4H-SiC
- 2014
-
Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 14:8, s. 4104-4110
-
Tidskriftsartikel (refereegranskat)abstract
- 4H-SiC epilayers grown by standard and chlorinated chemistry were analyzed for their minority carrier lifetime and deep level recombination centers using time-resolved photoluminescence (TRPL) and standard deep level transient spectroscopy (DLTS). Next to the well-known Z(1/2) deep level a second effective lifetime killer, RB1 (activation energy 1.05 eV, electron capture cross section 2 x 10(-16) cm(2), suggested hole capture cross section (5 +/- 2) x 10(-15) cm(2)), is detected in chloride chemistry grown epilayers. Junction-DLTS and bulk recombination simulations are used to confirm the lifetime killing properties of this level. The measured RB1 concentration appears to be a function of the iron-related Fe1 level concentration, which is unintentionally introduced via the corrosion of reactor steel parts by the chlorinated chemistry. Reactor design and the growth zone temperature profile are thought to enable the formation of RB1 in the presence of iron contamination under conditions otherwise optimal for growth of material with very low Z(1/2) concentrations. The RB1 defect is either an intrinsic defect similar to RD1/2 or EH5 or a complex involving iron. Control of these corrosion issues allows the growth of material at a high growth rate and with high minority carrier lifetime based on Z(1/2) as the only bulk recombination center.
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| 24. |
- Booker, Ian Don, et al.
(författare)
-
Carrier lifetime in p- and n-type 4H-SiC
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Temperature-dependent time-resolved photoluminescence measurements made in the temperature range from 77 K to 1000 K on free-standing as grown n-type 4H-SiC and p-type 4H-SiC epilayers, which are either as-grown or annealed at 1000 °C, 1400 °C or 1700 °C, are analyzed. The development of the instantaneous carrier lifetime over temperature, calculated from the decay curves of all n- and p-type samples, is found to be identical in the entire temperature range. With increasing annealing temperature only the magnitude of the lifetime in p-type 4H-SiC decreases while the trend remains identical to that in the as-grown n-type sample. Annealing thus only increases the density of the main recombination center which appears to control lifetime in as-grown n- and p-type material. The results implies that the lifetime in all samples may be governed by the same intrinsic defect, which we suggest to be Z1/2.
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| 25. |
- Booker, Ian D., et al.
(författare)
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Chloride-based SiC growth on a-axis 4H-€“SiC substrates
- 2016
-
Ingår i: Physica. B, Condensed matter. - : Elsevier. - 0921-4526 .- 1873-2135. ; 480, s. 23-25
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract SiC has, during the last few years, become increasingly important as a power-device material for high voltage applications. The thick, low-doped voltage-supporting epitaxial layer is normally grown by CVD on 4° off-cut 4H–SiC substrates at a growth rate of 5 – 10 Ό m / h using silane (SiH4) and propane (C3H8) or ethylene (C2H4) as precursors. The concentrations of epitaxial defects and dislocations depend to a large extent on the underlying substrate but can also be influenced by the actual epitaxial growth process. Here we will present a study on the properties of the epitaxial layers grown by a Cl-based technique on an a-axis (90° off-cut from c-direction) 4H–SiC substrate.
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| 26. |
- Booker, Ian Don, et al.
(författare)
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Comparison of post-growth carrier lifetime improvement methods for 4H-SiC epilayers
- 2012
-
Ingår i: Silicon Carbide And Related Materials 2011, Pts 1 And 2. - : Trans Tech Publications Inc.. - 9783037854198 ; , s. 285-288, s. 285-288
-
Konferensbidrag (refereegranskat)abstract
- We compare two methods for post-growth improvement of bulk carrier lifetime in 4H-SiC: dry oxidations and implantations with either 12C or 14N, followed by high temperature anneals in Ar atmosphere. Application of these techniques to samples cut from the same wafer/epilayer yields 2- to 11-fold lifetime increases, with the implantation/annealing technique shown to give greater maximum lifetimes. The maximum lifetimes reached are ∼5 μs after 12C implantation at 600 °C and annealing in Ar for 180 minutes at 1500 °C. At higher annealing temperatures the lifetimes decreases, a result which differs from reports in the literature.
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| 27. |
- Booker, Ian Don, et al.
(författare)
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Donor and double donor transitions of the carbon vacancy related EH6/7 deep level in 4H-SiC
- 2016
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 119:23
-
Tidskriftsartikel (refereegranskat)abstract
- Using medium- and high-resolution multi-spectra fitting of deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS), optical O-DLTS and optical-electrical (OE)-MCTS measurements, we show that the EH6∕7 deep level in 4H-SiC is composed of two strongly overlapping, two electron emission processes with thermal activation energies of 1.49 eV and 1.58 eV for EH6 and 1.48 eV and 1.66 eV for EH7. The electron emission peaks of EH7 completely overlap while the emission peaks of EH6 occur offset at slightly different temperatures in the spectra. OE-MCTS measurements of the hole capture cross section σp 0(T) in p-type samples reveal a trap-Auger process, whereby hole capture into the defect occupied by two electrons leads to a recombination event and the ejection of the second electron into the conduction band. Values of the hole and electron capture cross sections σn(T) and σp(T) differ strongly due to the donor like nature of the deep levels and while all σn(T) have a negative temperature dependence, the σp(T) appear to be temperature independent. Average values at the DLTS measurement temperature (∼600 K) are σn 2+(T) ≈ 1 × 10−14 cm2, σn +(T) ≈ 1 × 10−14 cm2, and σp 0(T) ≈ 9 × 10−18 cm2 for EH6 and σn 2+(T) ≈ 2 × 10−14 cm2, σn +(T) ≈ 2 × 10−14 cm2, σp 0(T) ≈ 1 × 10−20 cm2 for EH7. Since EH7 has already been identified as a donor transition of the carbon vacancy, we propose that the EH6∕7 center in total represents the overlapping first and second donor transitions of the carbon vacancy defects on both inequivalent lattice sites.
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| 28. |
- Booker, Ian Don, et al.
(författare)
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Electron and hole capture cross sections of deep levels accessible by DLTS and MCTS in p-type 4H-SiC
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The effective electron (σn(T)) and hole (σn(T)) capture cross sections of the electrically active deep levels HK0, HK2, LB1 and EM1 found in as-grown, high temperature annealed and oxidized p-type 4H-SiC were measured by deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS) and optical-electrical MCTS and DLTS (OE-MCTS and EO-DLTS) in an effort to determine the potential recombination centers in p-type material. Additionally, we also find the D-center, and the deep levels EH6/7, ON1 and ON2 in our samples, while the levels HK1, HK3 and HK4, reported in literature, are always below the detection limit. We further compare deep level concentrations and the timeresolved photoluminescence (TRPL) measured low injection (τLI) in samples annealed at up to 1920 °C. None of the detected deep levels possess σp(T):σn(T) ratios which could enable them to act as efficient recombination centers in the annealed epilayers, where τLI ranges from 1.2·10-6 s to less than 100·10-9 s. However, a clear anti-correlation between τLI and the EH6/7 concentration is found, which is linked to the main lifetime limiting center in n-type material, Z1/2, via their common origin, the carbon vacancy. Due to their large σp(T):σn(T) ratio, the Z1/2 deep levels are not detected by frontside illumination MCTS in p-type material. We thus conclude that the main lifetime limiting deep level(s) in p-type 4HSiC appear to be located in the upper half of the bandgap and are most likely either Z1/2, or other deep levels of intrinsic or partially intrinsic origin with a similar σp(T):σn(T) ratio.
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| 29. |
- Booker, Ian Don, et al.
(författare)
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High-Resolution Time-Resolved Carrier Lifetime and Photoluminescence Mapping of 4H-SiC Epilayers
- 2012
-
Ingår i: Materials Science Forum Vols 717 - 720. - : Trans Tech Publications Inc.. ; , s. 293-296
-
Konferensbidrag (refereegranskat)abstract
- We present a comparison between time-resolved carrier lifetime mappings of several samples and integrated near band edge intensity photoluminescence mappings using a pulsed laser. High-injection conditions and as-grown material are used, which generally allow for the assumption of a single exponential decay. The photoluminescence intensity under these circumstances is proportional to the carrier lifetime and the mappings can be used to detect lifetime-influencing defects in epilayers and give an estimate of the carrier lifetime variation over the wafer. Several examples for the defect detection capability of the system are given.
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| 30. |
- Bosma, Tom, et al.
(författare)
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Broadband single-mode planar waveguides in monolithic 4H-SiC
- 2022
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 131:2
-
Tidskriftsartikel (refereegranskat)abstract
- Color-center defects in silicon carbide promise opto-electronic quantum applications in several fields, such as computing, sensing, and communication. In order to scale down and combine these functionalities with the existing silicon device platforms, it is crucial to consider SiC integrated optics. In recent years, many examples of SiC photonic platforms have been shown, like photonic crystal cavities, film-on-insulator waveguides, and micro-ring resonators. However, all these examples rely on separating thin films of SiC from substrate wafers. This introduces significant surface roughness, strain, and defects in the material, which greatly affects the homogeneity of the optical properties of color centers. Here, we present and test a method for fabricating monolithic single-crystal integrated-photonic devices in SiC: tuning optical properties via charge carrier concentration. We fabricated monolithic SiC n-i-n and p-i-n junctions where the intrinsic layer acts as waveguide core, and demonstrate the waveguide functionality for these samples. The propagation losses are below 14 dB/cm. These waveguide types allow for addressing color centers over a broad wavelength range with low strain-induced inhomogeneity of the optical-transition frequencies. Furthermore, we expect that our findings open the road to fabricating waveguides and devices based on p-i-n junctions, which will allow for integrated electrostatic and radio frequency control together with high-intensity optical control of defects in silicon carbide.
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| 31. |
- Bourassa, Alexandre, et al.
(författare)
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Entanglement and control of single nuclear spins in isotopically engineered silicon carbide
- 2020
-
Ingår i: Nature Materials. - : NATURE RESEARCH. - 1476-1122 .- 1476-4660. ; 19:12, s. 1319-1325
-
Tidskriftsartikel (refereegranskat)abstract
- Isotope engineering of silicon carbide leads to control of nuclear spins associated with single divacancy centres and extended electron spin coherence. Nuclear spins in the solid state are both a cause of decoherence and a valuable resource for spin qubits. In this work, we demonstrate control of isolated(29)Si nuclear spins in silicon carbide (SiC) to create an entangled state between an optically active divacancy spin and a strongly coupled nuclear register. We then show how isotopic engineering of SiC unlocks control of single weakly coupled nuclear spins and present an ab initio method to predict the optimal isotopic fraction that maximizes the number of usable nuclear memories. We bolster these results by reporting high-fidelity electron spin control (F = 99.984(1)%), alongside extended coherence times (Hahn-echoT(2) = 2.3 ms, dynamical decouplingT(2)(DD) > 14.5 ms), and a >40-fold increase in Ramsey spin dephasing time (T-2*) from isotopic purification. Overall, this work underlines the importance of controlling the nuclear environment in solid-state systems and links single photon emitters with nuclear registers in an industrially scalable material.
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| 32. |
- Brosselard, P., et al.
(författare)
-
3.3 kV-10A 4H-SiC PiN diodes
- 2009
-
Ingår i: Materials Science Forum, Vols. 600-603. - : Trans Tech Publ.. ; , s. 991-994
-
Konferensbidrag (refereegranskat)abstract
- An innovative process has been developed by Linköping University to prepare the 4HSiC substrate surface before epitaxial growth. The processed PiN diodes have been characterized in forward and reverse mode at different temperature. The larger diodes (2.56 mm2) have a very low leakage current around 20 nA @ 500V for temperatures up to 300°C. A performant yield (68%) was obtained on these larger diodes have a breakdown voltage superior to 500V. Electroluminescence characteristics have been done on these devices and they show that there is no generation of Stacking Faults during the bipolar conduction.
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| 33. |
- Brosselard, P, et al.
(författare)
-
Comparison between 3.3kV 4H-SiC schottky and bipolar diodes
- 2008
-
Ingår i: IET Seminar Digest, Volume 2008, Issue 2, 2008. - : IEE. - 9788001041390 ; , s. 87-91
-
Konferensbidrag (refereegranskat)abstract
- Silicon Carbide Schottky and bipolar diodes have been fabricated with a breakdown voltage of 3.3kV. Diodes have been packaged and measured up to 300°C. The Schottky diode shows an increase of voltage drop with temperature and a reverse recovery charge independent from temperature. The PiN diode reverse recovery charge is ×20 at 300°C compared to that of the Schottky diode. 55% of the stressed bipolar diodes at 20A show a very small forward voltage drift. Theswitching losses of these stressed diodes are reduced by 20%. Substrate quality enhancement makes large SiC component fabrication possible (25mm 2 Schottky diodes) and bipolar components show very small tension drift with temperature.
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| 34. |
- Brosselard, P, et al.
(författare)
-
Low loss, large area 4.5 kV 4H-SiC PIN diodes with reduced forward voltage drift
- 2009
-
Ingår i: SEMICONDUCTOR SCIENCE AND TECHNOLOGY. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 24:9, s. 095004-
-
Tidskriftsartikel (refereegranskat)abstract
- 4H-SiC PIN diodes have been fabricated on a Norstel P+/N/N+ substrate with a combination of Mesa and JTE as edge termination. A breakdown voltage of 4.5 kV has been measured at 1 mu A for devices with an active area of 2.6 mm(2). The differential on-resistance at 15 A (600 A cm(-2)) was of only 1.7 m Omega cm(2) (25 degrees C) and 1.9 m Omega cm(2) at 300 degrees C. The reduced recovery charge was of 300 nC for a switched current of 15 A (500 V) at 300 degrees C. 20% of the diodes showed no degradation at all after 60 h of dc stress (25-225 degrees C). Other 30% of the diodes exhibit a reduced voltage shift below 1 V. For those diodes, the leakage current remains unaffected after the dc stress. Electroluminescence investigations reveal a very low density of stacking faults after the dc stress. The manufacturing yield evidences the efficiency of the substrate surface preparation and our technological process.
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| 35. |
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| 36. |
- Christle, David J., et al.
(författare)
-
Isolated electron spins in silicon carbide with millisecond coherence times
- 2015
-
Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 14:2, s. 160-163
-
Tidskriftsartikel (refereegranskat)abstract
- The elimination of defects from SiC has facilitated its move to the forefront of the optoelectronics and power-electronics industries(1). Nonetheless, because certain SiC defects have electronic states with sharp optical and spin transitions, they are increasingly recognized as a platform for quantum information and nanoscale sensing(2-16). Here, we show that individual electron spins in high-purity monocrystalline 4H-SiC can be isolated and coherently controlled. Bound to neutral divacancy defects(2,3), these states exhibit exceptionally long ensemble Hahn-echo spin coherence times, exceeding 1 ms. Coherent control of single spins in a material amenable to advanced growth and microfabrication techniques is an exciting route towards wafer-scale quantum technologies.
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| 37. |
- Christle, David J., et al.
(författare)
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Isolated Spin Qubits in SiC with a High-Fidelity Infrared Spin-to-Photon Interface
- 2017
-
Ingår i: Physical Review X. - : AMER PHYSICAL SOC. - 2160-3308. ; 7:2
-
Tidskriftsartikel (refereegranskat)abstract
- The divacancies in SiC are a family of paramagnetic defects that show promise for quantum communication technologies due to their long-lived electron spin coherence and their optical addressability at near-telecom wavelengths. Nonetheless, a high-fidelity spin-photon interface, which is a crucial prerequisite for such technologies, has not yet been demonstrated. Here, we demonstrate that such an interface exists in isolated divacancies in epitaxial films of 3C-SiC and 4H-SiC. Our data show that divacancies in 4H-SiC have minimal undesirable spin mixing, and that the optical linewidths in our current sample are already similar to those of recent remote entanglement demonstrations in other systems. Moreover, we find that 3C-SiC divacancies have a millisecond Hahn-echo spin coherence time, which is among the longest measured in a naturally isotopic solid. The presence of defects with these properties in a commercial semiconductor that can be heteroepitaxially grown as a thin film on Si shows promise for future quantum networks based on SiC defects.
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| 38. |
- Ciechonski, Rafal, et al.
(författare)
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Structural instabilities in growth of SiC crystals
- 2005
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 275:1-2, s. e461-e466
-
Tidskriftsartikel (refereegranskat)abstract
- Misoriented grains, which may occur on the growth front of 6H–SiC boules have been studied in relation to their appearance during sublimation growth. The effect was obtained by applying growth conditions at which the source powder was gradually approaching graphitisation and the vapour becoming C-rich. The high off-orientation of the grains is demonstrated through etching in molten KOH and transmission light optical microscopy. Micropipes propagating in the single crystal area and facing the misoriented grain have been studied, and it is shown that they may either be terminated at the grain or their propagation is altered to be parallel with the grain boundary. It has been found that the polytype of the grains may switch from 6H to 4H, which is explained by the change of the Si/C ratio in the vapour.
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| 39. |
- Cilibrizzi, Pasquale, et al.
(författare)
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Ultra-narrow inhomogeneous spectral distribution of telecom-wavelength vanadium centres in isotopically-enriched silicon carbide
- 2023
-
Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 14:1
-
Tidskriftsartikel (refereegranskat)abstract
- Spin-active quantum emitters have emerged as a leading platform for quantum technologies. However, one of their major limitations is the large spread in optical emission frequencies, which typically extends over tens of GHz. Here, we investigate single V4+ vanadium centres in 4H-SiC, which feature telecom-wavelength emission and a coherent S = 1/2 spin state. We perform spectroscopy on single emitters and report the observation of spin-dependent optical transitions, a key requirement for spin-photon interfaces. By engineering the isotopic composition of the SiC matrix, we reduce the inhomogeneous spectral distribution of different emitters down to 100 MHz, significantly smaller than any other single quantum emitter. Additionally, we tailor the dopant concentration to stabilise the telecom-wavelength V4+ charge state, thereby extending its lifetime by at least two orders of magnitude. These results bolster the prospects for single V emitters in SiC as material nodes in scalable telecom quantum networks. Several solid-state defect platforms have been proposed for application as a spin-photon interface in quantum communication networks. Here the authors report spin-selective optical transitions and narrow inhomogeneous spectral distribution of V centers in isotopically-enriched SiC emitting in the telecom O-band.
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| 40. |
- Civrac, Gabriel, et al.
(författare)
-
600 V PiN diodes fabricated using on-axis 4H silicon carbide
- 2012
-
Ingår i: Materials Science Forum Vol 717 - 720. - : Trans Tech Publications Inc.. ; , s. 969-972
-
Konferensbidrag (refereegranskat)abstract
- This paper reports the fabrication and electrical characterization of PiN diodes on an on-axis grown epitaxial layer. TCAD simulations have been performed in order to design their architecture. Some of these diodes have a breakdown voltage around 600 V. A comparison is made with similar diodes fabricated on off-cut grown layers. Computer simulations are used to explain lower breakdown voltages than those expected.
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| 41. |
- de las Casas, Charles F., et al.
(författare)
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Stark tuning and electrical charge state control of single divacancies in silicon carbide
- 2017
-
Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 111:26
-
Tidskriftsartikel (refereegranskat)abstract
- Neutrally charged divacancies in silicon carbide (SiC) are paramagnetic color centers whose long coherence times and near-telecom operating wavelengths make them promising for scalable quantum communication technologies compatible with existing fiber optic networks. However, local strain inhomogeneity can randomly perturb their optical transition frequencies, which degrades the indistinguishability of photons emitted from separate defects and hinders their coupling to optical cavities. Here, we show that electric fields can be used to tune the optical transition frequencies of single neutral divacancy defects in 4H-SiC over a range of several GHz via the DC Stark effect. The same technique can also control the charge state of the defect on microsecond timescales, which we use to stabilize unstable or non-neutral divacancies into their neutral charge state. Using fluorescence-based charge state detection, we show that both 975 nm and 1130 nm excitation can prepare their neutral charge state with near unity efficiency. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons. org/licenses/by/4.0/).
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| 42. |
- Dheilly, Nicolas, et al.
(författare)
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Measurement of Carrier Lifetime Temperature Dependence in 3.3kV 4H-SiC PiN Diodes Using OCVD Technique
- 2009
-
Ingår i: Silicon Carbide and Related Materials 2008. - : Trans Tech Publications Ltd. ; , s. 703-706
-
Konferensbidrag (refereegranskat)abstract
- This paper reports on the influence of temperature on the electrical carrier lifetime of a 3.3 kV 4H-SiC PiN diode processed with a new generation of SiC material. The Open Circuit Voltage Decay (OCVD) is used to evaluate ambipolar lifetime evolution versus temperature. The paper presents a description of the setup, electrical measurements and extraction fittings. The ambipolar lifetime is found to rise from 600 ns at 30 °C to 3.5 μs at 150 °C.
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| 43. |
- Frewin, Christopher L., et al.
(författare)
-
Silicon Carbide As a Robust Neural Interface (Invited)
- 2016
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Ingår i: GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 6. - : ELECTROCHEMICAL SOC INC. - 9781607687290 ; , s. 39-45
-
Konferensbidrag (refereegranskat)abstract
- The intracortical neural interface (INI) could be a key component of brain machine interfaces (BMI), devices which offer the possibility of restored physiological neurological functionality for patients suffering from severe trauma to the central or peripheral nervous system. Unfortunately the main components of the INI, microelectrodes, have not shown appropriate long-term reliability due to multiple biological, material, and mechanical issues. Silicon carbide (SiC) is a semiconductor that is completely chemically inert within the physiological environment and can be micromachined using the same methods as with Si microdevices. We are proposing that a SiC material system may provide the improved longevity and reliability for INI devices. The design, fabrication, and preliminary electrical and electrochemical testing of an all-SiC prototype microelectrode array based on 4H-SiC, with an amorphous silicon carbide (a-SiC) insulator, is described. The fabrication of the planar microelectrode was performed utilizing a series of conventional micromachining steps. Preliminary electrochemical data are presented which show that these prototype electrodes display suitable performance.
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| 44. |
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| 45. |
- Ghezellou, Misagh, 1988-, et al.
(författare)
-
Influence of Different Hydrocarbons on Chemical Vapor Deposition Growth and Surface Morphological Defects in 4H‐SiC Epitaxial Layers
- 2024
-
Ingår i: Physica status solidi. B, Basic research. - : WILEY-V C H VERLAG GMBH. - 0370-1972 .- 1521-3951.
-
Tidskriftsartikel (refereegranskat)abstract
- Controlled epitaxial growth of 4H-SiC is essential for advancing both power electronics and quantum technologies. This study explores how different carbon sources—methane and propane—affect the surface morphology of these epitaxial layers. By varying C/Si ratios and using the two mentioned hydrocarbons as the carbon source in chloride-based epitaxial growth of 4H-SiC layers, it is unveiled that methane results in an exceptionally smooth surface. However, it pronounces surface irregularities such as short step bunching and dislocation-related etch pits. Moreover, methane amplifies the overgrowth of triangular defects with the 4H polytype. In contrast, the introduction of propane causes a step-bunched surface together with inclined line-like surface morphological defects. Notably, a majority of the triangular defects exhibit a pure 3C character without an overgrown 4H polytype. It is shown that these outcomes could be attributed to different sticking coefficients and diffusivity of the molecular species resulting from different carbon sources on the 4H-SiC surface during the epitaxial growth. This research also uncovers the underlying origins and mechanisms responsible for various surface morphological defects.
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| 46. |
- Ghezellou, Misagh, 1988-, et al.
(författare)
-
The role of boron related defects in limiting charge carrier lifetime in 4H–SiC epitaxial layers
- 2023
-
Ingår i: APL Materials. - : American Institute of Physics (AIP). - 2166-532X. ; 11:3
-
Tidskriftsartikel (refereegranskat)abstract
- One of the main challenges in realizing 4H–SiC (silicon carbide)-based bipolar devices is the improvement of minority carrier lifetime in as-grown epitaxial layers. Although Z1/2 has been identified as the dominant carrier lifetime limiting defect, we report on B-related centers being another dominant source of recombination and acting as lifetime limiting defects in 4H–SiC epitaxial layers. Combining time-resolved photoluminescence (TRPL) measurement in near band edge emission and 530 nm, deep level transient spectroscopy, and minority carrier transient spectroscopy (MCTS), it was found that B related deep levels in the lower half of the bandgap are responsible for killing the minority carriers in n-type, 4H–SiC epitaxial layers when the concentration of Z1/2 is already low. The impact of these centers on the charge carrier dynamics is investigated by correlating the MCTS results with temperature-dependent TRPL decay measurements. It is shown that the influence of shallow B acceptors on the minority carrier lifetime becomes neutralized at temperatures above ∼422 K. Instead, the deep B related acceptor level, known as the D-center, remains active until temperatures above ∼570 K. Moreover, a correlation between the deep level concentrations, minority carrier lifetimes, and growth parameters indicates that intentional nitrogen doping hinders the formation of deep B acceptor levels. Furthermore, tuning growth parameters, including growth temperature and C/Si ratio, is shown to be crucial for improving the minority carrier lifetime in as-grown 4H–SiC epitaxial layers.
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| 47. |
- Gogova, Daniela, et al.
(författare)
-
Epitaxial growth of β -Ga 2 O 3 by hot-wall MOCVD
- 2022
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 12:5, s. 055022-055022
-
Tidskriftsartikel (refereegranskat)abstract
- The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and highperformance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth ofβ-Ga2O3. Epitaxial β-Ga2O3 layers at high growth rates (above 1 μm/h), at low reagent flows, and at reduced growth temperatures(740 ○C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. Thehot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial β-Ga2O3 layers are demonstrated with a 201 ¯rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown (201) ¯ β-Ga2O3 substrates, indicative ofsimilar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be furtherexplored for the fabrication of β-Ga2O3
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| 48. |
- Gogova, Daniela, 1967-, et al.
(författare)
-
Epitaxial growth of β-Ga2O3 by hot-wall MOCVD
- 2022
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 12:5
-
Tidskriftsartikel (refereegranskat)abstract
- The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and high performance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth of beta-Ga2O3. Epitaxial beta-Ga2O3 layers at high growth rates (above 1 mu m/h), at low reagent flows, and at reduced growth temperatures (740 degrees C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. The hot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial beta-Ga2O3 layers are demonstrated with a 201 rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown (201) beta-Ga2O3 substrates, indicative of similar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be further explored for the fabrication of beta-Ga2O3.
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| 49. |
- Hassan, Jawad, et al.
(författare)
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Influence of Growth Mechanism on Carrier Lifetime in on-axis Homoepitaxial Layers of 4H-SiC
- 2012
-
Ingår i: Materials Science Forum Vols 717 - 720. - : Trans Tech Publications Inc.. ; , s. 157-160
-
Konferensbidrag (refereegranskat)abstract
- In this report we present homoepitaxial growth of 4H-SiC on Si-face, nominally on-axis substrates with diameters up to 76 mm in a hot-wall chemical vapor deposition reactor. A comparatively low carrier lifetime has been observed in these layers; local variations in carrier lifetime are different from standard epilayers on off-cut substrates. The properties of the layers were studied with focus on charge carrier lifetime and its correlation with starting growth conditions, inhomogeneities of surface morphology and different growth mechanisms.
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| 50. |
- Hassan, Jawad, et al.
(författare)
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Optically Detected Temperature Dependences of Carrier Lifetime and Diffusion Coefficient in 4H- and 3C-SiC
- 2011
-
Ingår i: Materials Science Forum (Volumes 679 - 680). - : Trans Tech Publications Inc.. ; , s. 205-208
-
Konferensbidrag (refereegranskat)abstract
- Free carrier dynamics has been studied in 4H- and 3C-SiC in a wide temperature range using time-resolved photoluminescence, free carrier absorption, and light induced transient grating techniques. Considerably high carrier lifetime was observed in 3C-SiC epitaxial layers grown on 4H-SiC substrates using hot-wall CVD with respect to previously reported values for 3C-SiC grown either on Si or on 6H-SiC substrates. The temperature dependences of carrier lifetime and diffusion coefficient for 4H- and 3C-SiC were compared. Shorter photoluminescence decay time with respect to free carrier absorption decay time was observed in the same 4H-SiC sample, while these techniques revealed similar trends in the carrier lifetime temperature dependencies. However, the latter dependences for hot-wall CVD-grown 3C layers were found different if measured by time resolved photoluminescence and free carrier absorption techniques.
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