| 1. |
- Andersson, Thorvald, 1946, et al.
(författare)
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Macroscopic defects in GaN/AlN multiple quantum well structures grown by MBE on GaN templates
- 2009
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Ingår i: Microelectronics Journal. - : Elsevier BV. - 0026-2692. ; 40:2, s. 360-362
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Tidskriftsartikel (refereegranskat)abstract
- We have used MBE to grow in AlN/GaN superlattices, with different number of periods, on 2.5-mu m-thick MOVPE-GaN templates to study the development of defects such as surface deformation due to strain. After growth the samples were studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), XRD and Fourier transform infrared spectroscopy (FT-IR). The strain increased with the number of quantum wells (QWs) and eventually caused defects such as microcracks visible by optical microscopy at four or more QW periods. High-resolution TEM images showed shallow recessions on the surface (surface deformation) indicating formation of microcracks in the MQW region. The measured intersubband (IS) absorption linewidth from a four period structure was 97 meV, which is comparable with the spectrum from a 10 period structure at an absorption energy of similar to 700 meV. This indicates that the interface quality of the MQW is not substantially affected by the presence of cracks.
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| 2. |
- Baroni, Mpma, et al.
(författare)
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Modeling and gradient pattern analysis of irregular SFM structures of porous silicon
- 2006
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Ingår i: Microelectronics Journal. - : Elsevier BV. - 0026-2692. ; 37:4, s. 290-294
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Tidskriftsartikel (refereegranskat)abstract
- Technological applications in opto-electronic devices have increased the interest in characterizing porous silicon structure patterns. Due to its physical properties, solutions from KPZ 2D are adopted to simulate the structure of porous material interface whose spatial characteristics are equivalent to those found in porous silicon samples. The analysis of the simulated and real scanning Force Microscopy (SFM) surfaces was done using the Gradient Pattern Analysis (GPA). We found that the KPZ 2D model presented asymmetry levels compatible with the irregular surfaces observed by means of SFM images of pi-Si.
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| 3. |
- Holtz, Per-Olof, 1951-, et al.
(författare)
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Effects of External Fields on the Excitonic Emission from Single InAs/GaAs Quantum Dots
- 2008
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Ingår i: Microelectronics Journal, Vol. 39. - Microelectronics Journal : Elsevier. ; , s. 331-334
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Konferensbidrag (refereegranskat)abstract
- A low-temperature micro-photoluminescence (μ-PL) investigation of InAs/GaAs quantum dots (QDs) exposed to a lateral external electric field is reported. It is demonstrated that the QDs PL signal could be increased several times by altering the external and/or the internal electric field. The internal field in the vicinity of the dots could be altered by means of an additional infra-red laser. We propose a model, which is based on an essentially faster lateral transport of the charge carriers achieved in an external electric field. Consequently, also the capture probability into the dots and subsequently the dot luminescence is also enhanced. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity measured in our experiment.
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| 4. |
- Karpyna, V A, et al.
(författare)
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Electron field emission from ZnO self-organized nanostructures and doped ZnO : Ga nanostructured films
- 2009
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Ingår i: Microelectronics Journal. - : Elsevier BV. - 0959-8324 .- 0026-2692. ; 40:2, s. 229-231
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Tidskriftsartikel (refereegranskat)abstract
- Self-organized ZnO nanostructures were grown by thermal decomposition of metalorganic precursors as well as by carbothermal reduction process. Nanostructured undoped and gallium-doped ZnO nanostructured films were deposited by plasma-enhanced chemical vapor deposition from metalorganic compounds. Electron field emission follows Fowler-Nordheim equation. Efficient electron emission was obtained from self-organized nanorstructures due to their geometric shape. Enhanced field emission from ZnO:Ga nanorstructured films in comparison with undoped ZnO films is obliged to lowering work function at doping by gallium.
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| 5. |
- Klason, P, et al.
(författare)
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Fabrication and characterization of p-Si/n-ZnO heterostructured junctions
- 2009
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Ingår i: MICROELECTRONICS JOURNAL. - : Elsevier BV. - 0026-2692. ; 40:4-5, s. 706-710
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Tidskriftsartikel (refereegranskat)abstract
- In this paper ZnO nanorods and nanodots (with and without a SiO2 buffer layer) were grown on p-Si, forming p-n heterojunctions. The nanorod devices showed no visible electroluminescence (EL) emission but showed rectifying behavior. Covering around 60% of the length of the nanorods with PMMA produced an ideality factor of 3.91 +/- 0.11 together with a reverse saturation current of 6.53 +/- 4.2 x 10(-8) A. Up to two orders of magnitude rectification was observed for the current at bias -3 and 3 V. The nanodot devices showed EL emission under forward bias conditions. It seems that the buffer layer increased both the stability and efficiency of the devices, since the buffer layer device could operate at larger applied voltage and showed EL emission under reverse bias.
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| 6. |
- Norström, H., et al.
(författare)
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Formation of a buried collector layer in RF-bipolar devices by ion implantation
- 2006
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Ingår i: MICROELECTRONICS JOURNAL. - : Elsevier BV. - 0026-2692. ; 37:11, s. 1366-1371
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Tidskriftsartikel (refereegranskat)abstract
- High-dose implantation of arsenic (As) buried collector layer formation for bipolar/BiCMOS processes has been studied. Wafers with and without screen oxide were subjected to high-dose implants with different energies. Some wafers were given a low-temperature anneal before XTEM and SIMS analyses. Defects observed after As implants of 6E15 cm(-2) through screen oxide after low-temperature anneal were annihilated at the subsequent high-temperature steps, but the direct implant of As into the silicon is preferred since fewer defects are generated and there is no knock-on of oxygen into the material. Fabricated devices showed excellent electrical performance. However, the upper limit (dose and/or energy) at which perfect recrystallization does no longer occur has not been defined and the process limit is consequently not established.
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| 7. |
- Peibst, R., et al.
(författare)
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PECVD grown Ge nanocrystals embedded in SiO(2) : From disordered to templated self-organization
- 2009
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Ingår i: MICROELECTRONICS JOURNAL. - : Elsevier BV. - 0026-2692. ; 40:4-5, s. 759-761
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Tidskriftsartikel (refereegranskat)abstract
- We present a new "templated self-organization" method for the preparation of Ge nanocrystals in SiO(2) that combines a bottom-up with a top-down approach for nanostructuring. Ge nanocrystals are formed by self-organization induced by thermal annealing of thin Ge films embedded ill SiO(2) whose areas are predefined by nanoimprint patterning. Thus Much smaller Structure sizes call be achieved than by pure nanostructuring and touch more regular structures call be prepared than by pure self-organization. in particular, the method enables the generation of Ge nanocrystals of equal size at predefined vertical and lateral positions thus facilitating the fabrication of nanoscaled devices due to the Suppression of Structural fluctuations.
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| 8. |
- Persson, Clas, et al.
(författare)
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X-ray absorption and emission spectroscopy of ZnO nanoparticle and highly oriented ZnO microrod arrays
- 2006
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Ingår i: Microelectronics Journal. - : Elsevier BV. - 0026-2692. ; 37:8, s. 686-689
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structures of ZnO nanoparticles and microrod arrays are studied by 0 Is X-ray absorption spectroscopy (XAS) and O K alpha X-ray emission spectroscopy (XES). We show that the present LDA +U-SIC calculation approach is suitable to correct the LDA self-interaction error of the cation d-states. The atomic eigenstates of 3d in zinc and 2p in oxygen are energetically close, which induces strong Zn-3d-O-2p hybridization. This anomalous valence band cation-d-anion-p hybridization is affected when the localization of the Zn 3d-states is taken into account. Experimentally, the XES spectra show energy dependence in the spectral shape revealing selected excitations to the Zn 3d, 4s and 4p states, hybridized with 0 2p states. Strong anisotropic effects are observed for the highly oriented ZnO rods, but not for the isotropic spherical nanoparticles. The nanostructured ZnO has primarily bulk XAS and XES properties.
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| 9. |
- Pettersson, Håkan, et al.
(författare)
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Photocurrent spectroscopy on self-assembled InAs quantum dots embedded in InP
- 2005
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Ingår i: Microelectronics Journal. - Amsterdam : Elsevier. - 0026-2692. ; 36:3-6, s. 227-230
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we report on an overview of recent results from Fourier transform photocurrent (FTPC) measurements in the infrared spectral region on ensembles of self-assembled InAs quantum dots embedded in a matrix of InP. In interband PC, clear signals related to the dots are observed. Comparing the PC- and PL spectra, we observe that the fundamental transition is absent in the PC spectra, which we interpret in terms of Pauliblocking due to a filled electron ground state of the dots. Our results furthermore suggest that an Auger process is involved in forming the interband PC signal. In intersubband PC, peaks related to transitions from the dots' ground- and first excited states to the conduction band of the matrix are observed. Using a novel approach of combining FTPC with illumination from an additional external non-modulated light source, we have measured the spectral distribution of photoionization of excitons in quantum dots and found an exciton binding energy in good agreement with theoretical calculations.
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| 10. |
- Shen, Meigen, et al.
(författare)
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Robustness enhancement through chip-package co-design for high-speed electronics
- 2005
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Ingår i: Microelectronics Journal. - : Elsevier BV. - 0959-8324 .- 0026-2692. ; 36:9, s. 846-855
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Tidskriftsartikel (refereegranskat)abstract
- The low interaction between chip and package design has an increasingly limiting effect on the system performance. In this paper, the chip-package co-design flow is presented. We address robustness enhancement under the package and interconnection constraints as well as process, voltage, and temperature (PVT) variations by using impedance control, optimal pins assignment and transmitter equalization. From the simulation results we find that without on-chip digital compensation circuit, the variation of the driver's output impedance is 37% under different PVT conditions. However, it is only 5% when digital compensation circuit is used. Through optimal pins assignment the effective inductance of the pins is reduced. When power and ground pins are used as shielding pins, crosstalk is also decreased by 10 dB. Transmitter equalization effectively decreases inter-symbol interference caused by interconnection attenuation and dispersion. In our design example we find that without equalization the eye-diagram is almost closed at the receiver end. On the other hand with one-tap pre-emphasis equalization the eye-diagram is open and has a height of 90 mV and a width of 140 ps. It is also found that there is a clear optimal window for high data rate in this design. Without a chip-package co-design such an optimal window will not be found.
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