Doping of amorphous silicon by potassium ion implantation

Abstract

Abstract Highly efficient n-type doping of hydrogenated amorphous silicon films has been achieved by ion implantation of potassium. A high dark conductivity, after implantation and annealing at the optimal temperature, could be obtained over the entire range of concentrations investigated (1018−4 × 1020cm−3). Post-hydrogenation with a Kaufmann ion source produced an increase in conductivity by a factor of up to four. The effect is opposite to that found in phosphorus-implanted samples, in which a decrease in dark conductivity after post-hydrogenation was observed. The highest conductivity obtained without microcry-stallization of the film was 1·6 × 10−l Ω−1 cm−1. The conductivities of potassium-doped samples were higher than those of phosphorus-implanted samples by two orders of magnitude at high concentrations and four orders of magnitude at Iow concentrations. Thermal equilibration experiments were carried out on both annealed and post-hydrogenated samples which confirmed that the eauilibration behaviou...