Electron transport properties of n-type bismuth modified a-Ge₂₀Se₇₀ films

Abstract

The addition of nearly 11 at.% Bi to amorphous Ge₂₀Se₇₀ films results in an increase in the room temperature conductivity by several orders of magnitude, a transition from p-to n-type conduction, a decrease in the optical gap from 1.85 to 1.15 eV, and a large decrease in the electrical activation energy from 0.82 to 0.09 eV. The optical and electrical data suggest that the addition of bismuth produces localized states near the conduction band edge so that the electrical transport is due to the hopping of electrons after being excited into localized states at the conduction band edge.