Effect of interface defects on the response time of a-Si:Ha-SiC:H superlattices

Abstract We have measured the influence on the response time of interface defects between ultrathin layers of hydrogenated amorphous silicon (a-Si:H) and silicon carbon alloys (a-SiC:H) using a series of a-Si:H a-SiC:H superlattices. In addition, majority and minority carrier transport parallel to the layers was analyzed by photoconductivity and ambipolar diffusion length measurements using the steady-state photocarrier grating technique. Numerical simulation of transport perpendicular to the layers rules out a decisive role of carrier drift towards interfaces. Based on carrier diffusion we obtain an estimate of the interface recombination velocity. Electrons are found to be affected more strongly by interfaces than holes, which suggests a strong increase of conduction band tail slope with decreasing sublayer thickness.