Some effects of boron and phosphorus doping on the properties of SiC:H films prepared using electron cyclotron resonance-chemical vapor deposition

Abstract

Hydrogenated silicon carbide films (SiC:H) were deposited using the electron cyclotron resonance chemical vapor deposition 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 deposition rate, optical band gap 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 all amorphous and the band gap decreases as the diborane level is increased, whereas films deposited at a high microwave power of 800 W at low diborane levels are highly conductive and contain the silicon microcrystalline phase. These films become amorphous as the diborane level is increased, while the optical band gap 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 band gap, suggesting that good phosphorus doping efficiency can be achieved in films that contain the silicon microcrystalline phase (mc-SiC:H).