Structural, electrical and optical characterization of N- and P-type SiC:H films deposited using ECR-CVD

Abstract

Hydrogenated silicon carbide films (SiC:H) were deposited using the electron cyclotron resonance chemical vapour deposition (ECR-CVD) method from a mixture of methane, silane and hydrogen, and using diborane and phosphine as doping gases. The effects of changes in the diborane and phosphine levels on the optical bandgap and conductivity were investigated. In the case of boron-doped films, there is evidence from Raman scattering analysis to show that films deposited at a low microwave power of 150 W were largely amorphous and the bandgap decreases as the diborane levels are highly conductive and contains the whereas films deposited at a high microwave power of 800 W at low diborane levels are highly conductive and contains the silicon microcrystalline phase. These films become amorphous as the diborane level is increased, while the optical bandgap remains relatively unaffected throughout the entire range of diborane levels investigated. In the case of phosphorus-doped films, Raman scattering analysis showed that the deposition conditions strongly influence the structural, optical and electrical properties of the SiC:H films. Unlike boron doping, doping with phosphorus can have the effect of increasing the silicon microcrystalline phase in the SiC:H films which were prepared at low (150 W) and high (600 W) microwave powers. Films prepared at high microwave power showed only small variations in the optical bandgap, suggesting that good phosphorus doping efficiency can be achieved in films which contain the silicon microcrystalline phase (mc-SiC:H).