Electronic properties of intrinsic and doped amorphous silicon carbide films

Abstract

Hydrogenated amorphous silicon carbide (a-SiC x : H) films have shown excellent surface passivation of crystalline silicon. With the aim of large area deposition of these films the influence of the rf plasma power was investigated. It is found that homogenous deposition with effective surface recombination velocity lower than 100 cms − 1 is possible up to 6″ diameter in a simple parallel plate reactor by optimizing deposition parameters. For application in solar cell processes the conductivity of these a-SiC x : H films might become of importance since good surface passivation results from field-effect passivation which needs an insulating dielectric layer. Therefore, the temperature dependence of the dark dc conductivity of these films was investigated in the temperature range from − 20 to 260 °C. Two transition temperatures, T s≈80 °C and T s≈170 °C, were found where conductivity increases, resp. decreases over-exponential. From Arrhenius plots activation energy ( E a) and conductivity pre-factor ( σ 0) were calculated for a large number of samples with different composition. A correlation between E a and σ 0 was found giving a Meyer–Neldel relation with a slope of 59 mV, corresponding to a material characteristic temperature T m = 400 °C, and an intercept at σ 00 = 0.1 Ω − 1 cm − 1 .