Surface passivation of p-type crystalline Si by plasma enhanced chemical vapor deposited amorphous SiCx:H films

Excellent passivation properties of intrinsic amorphous silicon carbide (a-SiCx:H) films deposited by plasma enhanced chemical vapor deposition on single-crystalline silicon (c-Si) wafers have been obtained. The dependence of the effective surface recombination velocity, S-eff, on deposition temperature, total pressure and methane (CH4) to silane (SiH4) ratio has been studied for these films using lifetime measurements made with the quasi-steady-state photoconductance technique. The dependence of the effective lifetime, tau (eff,) on the excess carrier density, Deltan, has been measured and also simulated through a physical model based on Shockley-Read-Hall statistics and an insulator/semiconductor structure with fixed charges and band bending. A S-eff at the a-SiCx:H/c-Si interface lower than 30 cm s(-1) was achieved with optimized deposition conditions. This passivation quality was found to be three times better than that of noncarbonated amorphous silicon (a-Si:H) films deposited under equivalent conditions. v (C) 2001 American Institute of Physics.