Electron mobility in hydrogenated amorphous silicon under single and double injection

Abstract

A recent suggestion that the band mobility of electrons in hydrogenated amorphous silicon (a-Si:H) is larger under high-level double-injection than under single-injection conditions because of the neutralization of charged defect states in the former case is tested by studying the transit time of carriers under both conditions. It is found that the drift mobility at 320 K in a device allowing the injection only of electrons is approximately 1 cm2/V s, consistent with the results of many earlier investigations. On contrast, the 320 K drift mobility in a device in which double injection of both electrons and holes occurs is estimated to be about 15 cm2/V s, more than an order of magnitude larger. We conclude that the band mobility of electrons in a-Si:H is indeed considerably larger in the presence of high-level double injection than under single-injection conditions.