Analysis of the oscillating photocarrier grating technique

Abstract

In this paper we present a complete theoretical analysis of the oscillating photocarrier grating (OPG) method, starting from the generalized equations that describe charge transport and recombination under oscillating grating illumination conditions. The solution of these equations allows us to implement a calculation reproducing the experimental OPG curves. We study both experimentally and from our calculations the dependence of the OPG curves on different external parameters, such as the applied electric field, grating period and illumination intensity. We find that the response of the sample is linked to a characteristic time of the material, which could be the dielectric relaxation time or the small signal lifetime depending on the regime at which the experiment is performed. Therefore, the OPG technique provides a simple method to estimate these parameters. In addition, we demonstrate that the small signal lifetime provides information on the density of states of the material.