Photoconductivity Decay Characteristics of Undoped p-Type CuGaS2

Abstract

Photoconductivity decay characteristics of undoped p-type CuGaS2 were measured at temperatures between 100 and 340 K to determine the carrier relaxation mechanisms correlated with some transition peaks in the excitation spectra. A direct recombination of free electrons and holes is observed for the intrinsic peak. For the extrinsic peak via a shallow donor, excited holes relax rapidly with a temperature-independent decay time of 5-8 µs, followed by electron decay with a temperature-dependent decay time. This results in a major recombination path between the conduction band and a shallow acceptor state. For the broad peak via a deep donor, a remarkable increase in decay time occurs above 250 K. This phenomenon is primarily caused by thermal emptying of the shallow acceptor state.