Papers by Keyword: Threading Dislocation

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Authors: Md. Arafat Hossain, Md. Rafiqul Islam
Abstract: This paper presents a theoretical calculation of misfit dislocation and strain relaxation in compositionally step graded InxGa 1-x N grown on GaN using the total dislocation energy at each interface. The results also compared with uniform layer of In 0.17 Ga 0.83 N and In 0.14 Ga 0.86 N grown differently on GaN. Due to having residual strain and a step increase in indium composition a lower misfit strain in upper layers and hence larger critical thickness at each interface has been reported. These effects significantly reduced the misfit dislocations from 2.6×105 cm-1 to 9.5×104 cm-1 in step graded In 0.14 Ga 0.86 N(500nm)/In 0.09 Ga 0.91 N(100nm)/In 0.05 Ga 0.95 N(100nm)/GaN layers instead of a uniform In 0.14 Ga 0.86 N(700nm)/GaN. A small residual strain of 0.0007 after 700 nm graded layer thickness has been reported with 87.04% strain relaxation.
Authors: Laurent Souriau, V. Terzieva, Marc Meuris, Matty Caymax
Authors: H.M. Liaw, R. Venugopal, J. Wan, R. Doyle, P. Fejes, Mark J. Loboda, M.R. Melloch
Authors: Sha Yan Byrapa, Fang Zhen Wu, Huan Huan Wang, Balaji Raghothamachar, Gloria Choi, Shun Sun, Michael Dudley, Edward Sanchez, Darren M. Hansen, Roman Drachev, Stephan G. Mueller, Mark J. Loboda
Abstract: A review is presented of Synchrotron White Beam X-ray Topography (SWBXT) studies of stacking faults observed in PVT-Grown 4H-SiC crystals. A detailed analysis of various interesting phenomena were performed and one such observation is the deflection of threading dislocations with Burgers vector c/c+a onto the basal plane and associated stacking faults. Based on the model involving macrostep overgrowth of surface outcrops of threading dislocations, SWBXT image contrast studies of these stacking faults on different reflections and comparison with calculated phase shits for postulated fault vectors, has revealed faults to be of basically four types: (a) Frank faults; (b) Shockley faults; (c) Combined Shockley + Frank faults with fault vector s+c/2; (d) Combined Shockley + Frank faults with fault vector s+c/4.
Authors: Kendrick X. Liu, X. Zhang, Robert E. Stahlbush, Marek Skowronski, Joshua D. Caldwell
Abstract: Material defects such as Si-core and C-core partial dislocations (PDs) and threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are being investigated for their contributions to device performances in 4H-SiC. Non-destructive electroluminescence and photoluminescence techniques can be powerful tools for examining these dislocations. In this report, these techniques were used to reveal the different spectral characteristics for the mentioned dislocations. At higher injection levels, both the Si-core and C-core PDs possessed a spectral peak at 700 nm. However, at lower injection levels, the spectral peak for the Si-core PD remained at 700 nm while the peak for the C-core moved to longer wavelengths. For the threading dislocations, TSDs possessed a peak between 800 and 850 nm while the TEDs possessed a peak at 600 nm independent of the injection levels.
Authors: Yuji Yamamoto, S. Harada, Kazuaki Seki, Atsushi Horio, Takato Mitsuhashi, Toru Ujihara
Abstract: We investigated the dislocation behaviors during the solution growth on Si-face and C-face off-axis 4H-SiC seed crystals by using synchrotron X-ray topography. On Si-face, almost all threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are converted into Frank-type defects and basal plane dislocations (BPDs), respectively. On the other hand, on C-face, TSDs were hardly converted. Some of TEDs were converted to BPDs and BPD-TED reconversion was often occurred. Therefore, to reduce density of threading dislocations in the grown crystal, it is better to use Si-face off-axis seed crystal.
Authors: Eddy Simoen, Cor Claeys, Eugenijus Gaubas, J.M. Rafí
Abstract: An overview is given of analytical techniques for the characterization of the electrical and transport parameters in thin (<1 µm) semiconductor layers. Some of these methods have been applied to the lifetime and diffusion length study in thin strain-relaxed buffer (SRB) layers of strained silicon (SSi) substrates, while a second group was dedicated to Silicon-on-Insulator (SOI) materials and devices. The employed techniques can be divided into two groups, whether a device structure (junction, MOS capacitor, MOSFET) is required or not. However, the MicroWave Absorption (MWA) technique can be used in both cases, making it a versatile tool to study both grown-in and processing-induced electrically active defects. The transport properties of SSi wafers are strongly determined by the density of threading and misfit dislocations, although the dependence of the recombination lifetime is weaker than expected from simple Shockley-Read-Hall (SRH) theory. This is related to the high injection regime typically employed, enabling the characterization of the 250-350 nm thick Si1-xGex layer only. At longer carrier decay times, multiple trapping events dominate that can be described by a stretched exponent approach, typical of disordered materials. For SOI substrates, transistor-based techniques will be demonstrated that enable to assess the generation or recombination lifetime in the thin silicon film (<100 nm). The lifetime can be severely degraded by irradiation or hot-carrier degradation. Finally, it will be shown that Generation-Recombination (GR) noise spectroscopy as a function of temperature allows identifying residual ion-implantation-damage related deep levels, which are otherwise hard to detect even by Deep Level Transient Spectroscopy (DLTS).
Authors: Michael Dudley, Huan Huan Wang, Fang Zhen Wu, Sha Yan Byrapa, Balaji Raghothamachar, Gloria Choi, Edward Sanchez, Darren M. Hansen, Roman Drachev, Stephan G. Mueller, Mark J. Loboda
Abstract: Synchrotron White Beam X-ray Topography studies are presented of dislocation behavior and interactions in a new generation of seventy-six millimeter diameter, 4H-SiC wafers grown using Physical Vapor Transport under specially designed low stress conditions. Such low stress growth conditions have enabled reductions of dislocation density by two or three orders of magnitude compared to the lowest previously reported levels [1]. In this paper, detailed topography analysis will be presented of the deflection of threading dislocations with Burgers vectors of c and c+a onto the basal plane leading to reductions of the density of such dislocations down to levels of ~187 cm-2. The deflection of the latter type of dislocations produces complex faulted defect configurations and models for their creation are presented and discussed.
Authors: D.H. Kang, Jae Chul Song, Dong Wook Kim, J.S. Kim, Kannappan Santhakumar, Cheul Ro Lee
Abstract: We report the microstructure and optical properties of gallium nitride (GaN) epilayers grown on lens shape patterned sapphire substrate (PSS) using metalorganic chemical vapor deposition (MOCVD) for various growth times. A lens shaped pattern was used to reduce the threading dislocation density and to improve optical emission efficiency. A scanning electron microscope (SEM) image shows flat and smooth surface of GaN grown on PSS at 80 min which could be achieved by lateral growth from the trench region. From the DCXRD spectra, full width at half maximun (FWHM) value was decreased with increasing growth time. FWHM of the sample grown at 80 min was 473.5 arc sec. This indicates there is an improvement in crystalline quality of the GaN grown on PSS as the growth time increases. From photoluminescence (PL) spectra, an increase in band edge emission intensity and a decrease in defect related yellow luminescence was observed for GaN on PSS as the growth time increased. From the PL spectra, FWHM was 82.2 meV at peak position 363.9 nm for the sample grown for 80 min. It is clearly seen that the threading dislocations can be reduced by lateral growth improving the light emission efficiency by internal light reflection on the lens surface for GaN grown on PSS.
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