Extrinsic photoresponse and photoluminescence of CuInSe2 crystals grown with a deviation from valence stoichiometry

Abstract

Extrinsic photoresponse spectra (T=300 K) and photoluminescence spectra (T=77 K) of CuInSe2 single crystals grown with the deviation from valence stoichiometry are studied for point defect identification. The main peaks of photoresponse and photoluminescence correlate each other. The characteristic spectral singularities at 1.00, 0.98–0.97, 0.94, 0.92–0.89, and 0.72 eV have been attributed to photoactive and radiative transitions through the donor (VSe,InCu) and acceptor (VCu,CuIn,Sei) levels. The shift of the extrinsic photoresponse peak to long wavelengths (0.92→0.89 eV) by the VSe point defect has been found at increasing deviation from valence stoichiometry ΔZ<0. The impurity subband formation has been suggested as very probable in the crystals with elevated ΔZ.