CO2 laser-assisted deposition of boron and phosphorus-doped hydrogenated amorphous silicon

Abstract

Gas‐phase doping of hydrogenated amorphous silicon by CO₂ laser‐assisted chemical vapor deposition of silane is reported. p‐type and n‐type doping has been achieved by adding controlled amounts of diborane or phosphine to the reacting mixture in a horizontal flowing gas reactor. Silane molecules decompose by direct resonant absorption of the laser radiation and contribute to the dissociation of the dopant molecules through collisional energy transfers. The occurrence of substitutional doping is confirmed by the change in the dark conductivity by several orders of magnitude as well as by the decrease of its activation energy with increasing dopant gas concentration.