Visible photoluminescence in hydrogenated amorphous silicon grown in microwave plasma from SiH4 strongly diluted with He

Abstract

Room temperature visible photoluminescence (PL) of wide-band gap hydrogenated amorphous silicon (a-Si:H) thin films prepared in SiH4 microwave plasma strongly diluted with He is reported. Films were characterized by means of optical and infrared absorption, hydrogen thermal desorption, and Raman scattering. The band gap of a-Si:H films varies within the interval 2.0–2.2 eV, corresponding PL maxima are located at 1.4–1.6 eV. The highest PL intensity was observed in samples with a position of H–Si–H symmetric stretching vibration of the –(SiH2)n– units near the frequency of 2100 cm−1. The strong evidence for two distinct types of PL processes is presented: one being linked with oligosilanes and the second one attributed to electron-hole recombination in tail states.