Intrinsic defects in high purity semi-insulating 6H SiC
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0911-B05-07
Intrinsic defects in high purity semi-insulating 6H SiC D. V. Savchenko1, E. N. Kalabukhova2, S. N. Lukin1, Tangali S. Sudarshan3, Yuri I. Khlebnikov4, William C. Mitchel5, and S. Greulich-Weber6 1 NASU, Institute of Semiconductor Physics, Pr. Nauki 45, Kiev, Kiev, 03028, Ukraine 2 NASU, Institute of Semiconductor Physics, Kiev, Kiev, 03028, Ukraine 3 Department of Electrical Engineering, University of South Carolina, Columbia, SC, 29208 4 Intrinsic Semiconductor Corp., 22660 Executive Dr., Suite 101, Dulles, VA, 20166 5 AFRL/MLPS, Air Force Research Laboratory, Wright Patterson AFB, OH, 45433-7707 6 Department of Physics, University of Paderborn, Paderborn, Germany, D-33098, Germany ABSTRACT Electron paramagnetic resonance (EPR) and photo EPR measurements were performed on undoped semi-insulating (SI) 6H SiC material grown by the physical vapor transport (PVT) method. EPR lines from a carbon-related surface defect, two photosensitive high temperature stable intrinsic defects with S=1/2 and shallow nitrogen and boron were observed. The EPR spectrum of the intrinsic defect labeled XX was observed in the dark and consists of three single lines XX1, XX2, XX3 due to three inequivalent sites in the 6H SiC. The second defect labeled PP appeared in EPR spectrum during photo-excitation of the SI 6H SiC and consisted of a single EPR line. The photo EPR data placed the energy level of the defects in the region EV + 1.24 1.29 eV.. The EPR parameters and symmetry behavior of XX agree well with those of the carbon vacancy-related Ky center observed in p-type electron irradiated 6H SiC and we tentatively identify the XX defect with VC+. The electronic processes occurring in undoped SI 6H SiC under photo-excitation are also described.
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INTRODUCTION Semi-insulating (SI) silicon carbide substrates are required for high power microwave devices and circuits based on SiC and GaN. SI properties of SiC can be achieved by introducing deep levels from either impurities or intrinsic defects into the material to compensate shallow donors and acceptors and pin the Fermi level near the middle of the bandgap. Intrinsic defects with deep levels are believed to be responsible for the SI properties of undoped material. Most of the intrinsic defects studied in SI SiC have energies ranging from 0.85 to 1.8 eV below the conduction band. But not all of these defects are temperature stable and desirable for SI SiC. Among the defects which are temperature stable and may be responsible for SI properties of high purity semi-insulating (HPSI) 4H SiC are the ID and X defects. ID with energy level of 1.79 eV below the conduction band was observed in p-type material and identified as the carbon vacancy in the single positive charge state, VC+ [1]. The X defect with energy 1.3 eV below the conduction band was observed in n- type HPSI 4H SiC and identified as the hydrogenated carbon vacancy (VC+H) [2]. Most of the study of intrinsic defects in SI SiC have been made on the 4H polytype due to its relatively wide availability but very little report
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