High-resolution photoinduced transient spectroscopy of defect centers in vanadium-doped semi-insulating SiC

High-resolution photoinduced transient spectroscopy (HRPITS) has been applied to studying deep-level defects controlling the charge compensation in semi-insulating (SI), vanadium-doped, bulk 6H– and 4H–SiC. The photocurrent relaxation waveforms were digitally recorded in the temperature range of 300–750 K and a new approach to extract the parameters of defect centers from the temperature-induced changes in the waveforms’ time constants has been implemented. It is based on a two-dimensional analysis using the numerical inversion of the Laplace transform. As a result, the images of spectral fringes depicting the temperature dependences of the emission rate of charge carriers for defect centers are created. For 6H–SiC:V, 11 deep defect centers with activation energies ranging from 660 to 1405 meV were resolved. For 4H–SiC:V, 13 deep traps with activation energies ranging from 560 to 1530 meV were detected. In the both polytypes, the predominant traps were found to be related to vanadium donors located at quasi-cubic and hexagonal lattice sites.