Picosecond Transient Grating Experiments on Hydrogenated Amorphous Silicon: A Model for Surface Quenching

Abstract

In this article we present a room temperature experimental study of the transport and surface quenching of optically generated charge carriers in thin-film hydrogenated amorphous silicon (a-Si:H). At low temperature (4.2 K), in high quality samples, the principal mechanism for carrier quenching is radiative recombination.^l Nonradiative processes such as Auger recombination and tunneling to defects play only a minor role.¹ However, it has been suggested² that surface effects play an important role at higher temperatures (77 K). Rehm et al.^2a examined the effects of sample thickness and wavelength (optical penetration depth) on the decay time of the luminescence. They found dramatic effects when the sample thickness or the optical penetration depth fell below 0.3 µm.