Papers by Keyword: Deep Center

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Authors: Sung Wook Huh, A.Y. Polyakov, Hun Jae Chung, Saurav Nigam, Marek Skowronski, E.R. Glaser, W.E. Carlos, Mark A. Fanton, N.B. Smirnov
Abstract: Deep electron and hole traps were studied in a series of high purity 6H-SiC single crystals grown by Halide Chemical Vapor Deposition (HCVD) method at various C/Si flow ratios and at temperatures between 2000 oC and 2100 oC. Characterization included Low Temperature Photoluminescence (LTPL), Deep Level Transient Spectroscopy (DLTS), Minority Carrier Transient Spectroscopy (MCTS), and Thermal Admittance Spectroscopy (TAS) measurements. Concentrations of all deep traps were shown to strongly decrease with increased C/Si flow ratio and with increased growth temperature. The results indicate that the majority of deep centers in 6H-SiC crystals grown by HCVD are due to native defects or complexes of native defects promoted by Si-rich growth conditions. The observed growth temperature dependence of residual donor concentration and traps density is explained by increasing the effective C/Si ratio at higher temperatures for the same nominal ratio of C and Si flows.
Authors: Qiang Li, A.Y. Polyakov, Marek Skowronski, Edward K. Sanchez, Mark J. Loboda, Mark A. Fanton, Timothy Bogart, Rick D. Gamble, N.B. Smirnov, Yuri N. Makarov
Abstract: For undoped 6H-SiC boules grown by physical vapor transport the variations of resistivity, of the type and density of deep electron and hole traps, and of the concentration of nitrogen and boron were studied as a function of position in the cross section normal to the growth axis and along the growth direction. It was observed that the concentrations of all deep electron and hole traps decreased when moving from seed to tail of the boule and from the center to the edge of the wafers. Modeling of the growth process suggests that the C/Si ratio increases in a similar fashion and could be responsible for observed changes. We also discuss the implications of such stoichiometry changes on compensation mechanisms rendering the crystals semi-insulating and on electrical uniformity of SI-SiC wafers.
Authors: Björn Magnusson, Peder Bergman, Erik Janzén
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