Doping Efficiency of Boron Trifluoride in the Preparation of P-Type Amorphous Silicon Carbide Thin Films

Abstract

The properties of two sets of samples, prepared using different RF-power densities and SiH₄/CH₄ proportions have been analysed as functions of BF₃ percentage with respect to SiH₄. In both cases, the optical gap E_G, after a slight initial decrease, remains at a value of approximately 2.1 eV without quenching in the doping ranges covered. At a high RF-power density of 88 mW/cm² using a gas mixture -containing 37% CH₄, conductivity improves only for dopant concentrations not beyond 9%, where it reaches a maximum value of 1 x 10^-8 (Ω cm)^-1. On the other hand, when a smaller RF-power density of 44 mW/cm² is applied to a gas mixture with 26% CH₄, no conductivity saturation is observed up to 15% BF₃. Tne best value obtained is - 2 x 10^-7 (Ω cm^-1). IR spectra allow to associate these features with film structural quality.