Visible Photoluminescence in Highly Photoconductive Hydrogenated Amorphous Silicon Deposited by Glow Discharge of SiH₄ Highly Diluted with He

Abstract

A wide-band-gap (> 2.0 eV) hydrogenated amorphous silicon (a-Si:H) film showing visible photoluminescence (PL) is obtained by rf glow-discharge decomposition of SiH 4 highly diluted with He. The PL and the structural properties of the a-Si:H are investigated. The He dilution leads to the extension of the band gap and the increase of the SiH 2 and ( SiH 2 ) n configurations in the film. The PL increases rapidly and blue-shifts consistently with the increase of the SiH 2 and (SiH 2 ) n configurations. By observation using transmission electron microscopy and Raman scattering, it is found that the film consists of uniform amorphous structure and includes no microcrystallites. The film exhibits a photoconductivity (under AM-1 light of 100 mW/cm 2 ) to dark conductivity ratio of over 10 6 in addition to a visible PL at room temperature. This new a-Si:H film has potential for application to an optical device with characteristics of both light emission and photosensitivity.