Trapping Recombination Process and Persistent Photoconductivity in Semi-Insulating 4H SiC

Abstract

The decay kinetics of a persistent photoconductivity (PPC) in undoped semi-insulating 4H SiC and intercenter charge transfer were studied with EPR, photo-EPR and optical admittance spectroscopy (OAS). A thermally activated charge transfer process that occurs in the dark has been observed. The PPC effect was observed directly in changes in the quality factor of the EPR cavity before and after illumination and by the decay of the OAS signal for deep levels, and indirectly by the excitation and decay of the nitrogen and boron EPR lines that were not observed in the dark before illumination. The decay kinetics of the PPC and photo-induced carrier capture by nitrogen and boron levels were found to follow a stretched exponential form. The PPC in the temperature range from 77 to 300K was found to be produced by a thermally induced charge transfer process involving deep trap levels.