Photoluminescence study of the carbon antisite-vacancy pair in 4H-and 6H-SiC

Two sets of prominent photoluminescence (PL) lines, called A and B here, in electron-irradiated and ion-implanted 4H-SiC have been investigated by low-temperature PL microscopy. From their spectral details, temperature dependence, emission energies, introduction, and annealing characteristics it is concluded that they arise from the neutral on-axis and off-axis carbon antisite-vacancy pairs (VCCSi)(0). Photoluminescence excitation spectroscopy has been used to derive an energy-level diagram for the B set of lines of 4H-SiC. The creation of these centers is demonstrated as a process that is sensitively dependent not only on the n or p doping of the material, as has been proposed but also on the temperature and the existence of inhomogeneous internal electric and strain fields. Samples of different purities from many different sources have been studied. Relatively impure, highly compensated doped samples exhibit very strong A and B PL and are referred to as AB material. Purer materials, largely uncompensated, called V here, that are n(N) or p(Al) doped, have photoluminescence from Si vacancy related defects but relatively little A or B intensity even after annealing at 900 degrees C. Similar sets of PL lines have also been observed in ion-implanted 4H-SiC and electron-irradiated 6H-SiC and investigated to a more limited extent. A wide range of different electron-irradiation conditions has been explored.