Annealing effect on optical and electronic properties of silicon rich amorphous silicon-carbide films

Abstract

A series of Si-rich amorphous silicon carbide (a-SiC:H) thin films were deposited in conventional plasma enhanced chemical vapor deposition system with various gas ratio R = [CH4]/[SiH4]. The microstructural, optical and electronic properties of as-deposited films were investigated in this study. It was found that optical band gap was linearly proportional to carbon content in the films and it could be controlled in a range of 1.8–2.4 eV by changing the gas ratio, R. Both dark and photo conductivities in room temperature were decreased with the increasing of carbon content in the films, and the photosensitivity reached as high as 104 for the film with the optical band gap of 1.96 eV. The as-deposited samples were subsequently annealed at the temperatures of 900°C and 1000°C. The formation of nanocrystalline silicon (nc-Si) dots in amorphous silicon carbide (a-SiC) host matrix was shown. The dark conductivity was enhanced by five orders of magnitude after annealing compared with that of as-deposited films. The result of temperature-dependent conductivity suggested that the property of carrier transport was dominated by conduction process between the extended states. Furthermore, room temperature electroluminescence (EL) was achieved from nc-Si/SiC system and the possible mechanism of radiative recombination mechanism was discussed.