Deep-Level Defects in Nitrogen-Doped 6H-SiC Grown by PVT Method
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1069-D07-04
Deep-Level Defects in Nitrogen-Doped 6H-SiC Grown by PVT Method Pawel Kaminski1, Michal Kozubal1, Krzysztof Grasza1,2, and Emil Tymicki1 1 Institute of Electronic Materials Technology, ul. Wólczyñska 133, Warszawa, 01-919, Poland 2 Institute of Physics Polish Academy of Sciences, Al. Lotników 32/46, Warszawa, 02-668, Poland ABSTRACT An effect of the nitrogen concentration on the concentrations of deep-level defects in bulk 6H-SiC single crystals is investigated. Six electron traps labeled as T1A, T1B, T2, T3, T4 and T5 with activation energies of 0.34, 0.40, 0.64, 0.67, 0.69, and 1.53 eV, respectively, were revealed. The traps T1A (0.34 eV) and T1B (0.40 eV), observed in the samples with the nitrogen concentration ranging from ~2x1017 to 5x1017 cm-3, are attributed to complexes formed by carbon vacancies located at various lattice sites and carbon antisites. The concentrations of traps T2 (0.64 eV) and T3 (0.67 eV) have been found to rise from ~5x1015 to ~1x1017 cm-3 with increasing the nitrogen concentration from ~2x1017 to ~2.0x1018 cm-3. These traps are assigned to complexes involving silicon vacancies occupying hexagonal and quasi-cubic sites, respectively, and nitrogen atoms. The trap T4 (0.69 eV) concentration also substantially rises with increasing the nitrogen concentration and it is likely to be related to complexes formed by carbon antisites and nitrogen atoms. The midgap trap T5 (1.53 eV) is presumably associated with vanadium contamination. The presented results show that doping with nitrogen involves a significant change in the defect structure of 6H-SiC single crystals. INTRODUCTION The properties of silicon carbide (SiC), in particular the wide band gap, excellent thermal conductivity and high breakdown electric field, make this material very attractive for manufacturing electron devices operating with high-power and high-frequency signals and capable of working at high temperatures. However, the quality of SiC single crystals in terms of application in advanced electronics is strongly affected by point defects formed during the crystal growth. These defects introduce deep energy levels in the band gap and may reduce the device performance acting as traps or recombination centers. Thus, the knowledge on the electronic properties of defect centers and their microscopic structure is of great importance to control the material quality. Accordingly to technological conditions, various types of point defects are formed in bulk SiC crystals grown by Physical Vapor Transport (PVT) method [1]. These include non-stoichiometric native defects, such as carbon VC and silicon VSi vacancies, vacancy pairs VCVSi, as well as antisite defects SiC and CSi in carbon and silicon sublattice. There are also extrinsic point defects due to contamination of crystals with residual atoms of various chemical elements, mainly with boron, aluminum, titanium and vanadium [2]. The theoretical analysis has shown that the partial pressure of silicon over the growing crystal plays an important role in the formation of Sch
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