Positron Annihilation and Electron Spin Resonance of Electron-Irradiated 3C-SiC
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POSITRON ANNIHILATION AND ELECTRON SPIN RESONANCE OF ELECTRON-IRRADIATED 3C-SiC HISAYOSHI ITOH*, MASAHITO YOSHIKAWA*, LONG WEI**, SHOICHIRO TANIGAWA**, ISAMU NASHIYAMA***a, SHUNJI MISAWA***, HAJIME OKUMURA***, AND SADAFUMI YOSHIDA*** *Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-12, Japan "**Institute of Materials Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305, Japan ***Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki 305, Japan a)Present address: Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-12, Japan ABSTRACT Positron annihilation and electron spin resonance (ESR) have been used to study defects introduced by 1MeV electron irradiation in n-type cubic silicon carbide (3C-SiC) epitaxially grown on Si by chemical vapor deposition. Positron annihilation measurements by using variable-energy positron beams indicated the narrowing of the Doppler-broadened energy spectrum of annihilation gamma-rays and the decrease in the effective diffusion length of positrons with increasing the electron fluence. These results show the formation of vacancy-type defects in 3C-SiC. An ESR spectrum labeled TI, which has an isotropic gvalue of 2.0029±+0.0001, was observed in electron irradiated 3C-SiC. The TI spectrum is interpreted by hyperfine interactions of paramagnetic electrons with 13C at four carbon sites and 2 9Si at twelve silicon sites, leads that the TI center results from a point defect at a silicon sublattice site. The production rate of the TI center was in good agreement with the carrier removal rate, indicating that the TI center captures an electron from the conduction band. All these results are accounted for by the introduction of negatively charged vacancies at silicon sublattice sites in 3C-SiC by the irradiation. INTRODUCTION Cubic silicon carbide (3C-SiC, zinc blende structure) has extreme thermal and chemical stability, and excellent electrical properties such as a high electron saturation velocity (2.7xlO7 cm/s) and an electron mobility (10 3cm 2/Vs) comparable with Si [1,2]. In recent years single crystalline 3C-SiC films large enough for the fabrication of planarstructure devices have been obtained on Si substrates by means of chemical vapor deposition (CVD). [3-5] Insulating layers have been also formed on the epilayers by conventional oxidation techniques. [6] The success in the growth of high-quality 3C-SiC having excellent physical properties by CVD stimulated the technological interest in these epilayers in connection with their application to electronic devices operated under severe environments, such as high-temperature and radiation fields. In fact a high-temperature operation [7] and a radiation tolerance [8] of 3C-SiC devices have been reported. For the development of 3C-SiC device application, it is indispensable to know microscopic structures, electronic levels, and annealing kinetics of defects in the material. The knowledge of these defect properties is also important from the fundamental point of view. Se
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