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Photoluminescence Spectroscopy of 4H- and 6H-SiC.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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Typical undoped bulk grown SiC shows n- or p-type conductivity due to residual impurities such as nitrogen, boron, or aluminum. In order to produce high resistivity material, vanadium can be used as a compensating dopant. Since vanadium is an amphoteric dopant in SiC, it produces either a donor state, V sub Si 4 3d sup 1 - V sub Si5 3d sup 0, or an acceptor state, V sub Si4 3d sup 1- V sub Si33d sup 2. Thus, vanadium doping can compensate both n- and p-type conductivity. In this work, vanadium doped and undoped 4H- and 6H-SiC grown by the sublimation method have been studied using low temperature photoluminescence PL. It was found that the luminescence observed between 0.85 to 0.95 eV of the intra-3d-shell transition of V sub Si4 3d sup 1 increased by an order of magnitude in samples intentionally doped with vanadium compared to samples unintentionally doped. In addition, the dominant visible-region luminescence was attributed to titanium which is an isoelectronic trap in SiC. The presence of a broad peak centered at approx. 1.90 eV in some samples is believed to be attributed to donor-acceptor pair recombination between a Ti sub Si-N sub c complex donor and the boron defect complex acting as an acceptor. Finally, the Ti sub Si-N sub c complex donor location in the bandgap of 6H-SiC is estimated to be E sub c-0.54 eV.
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