X-RAY PHOTOEMISSION ANALYSIS OF CHEMICALLY TREATED I-III-VI SEMICONDUCTOR SURFACES

Device-grade thin-film CuInSe2 was subjected to various chemical treat ments commonly used in photovoltaic device fabrication to determine th e resulting microscopic surface composition/morphology and the effect on II-VI CuInSe2 heterojunction formation. HCl (38%), Br-MeOH (<1% Br) , (NH4)(2)S, and NH4OH/thiourea solutions were used separately to modi fy the surface chemistry of the CuInSe? polycrystalline films. Scannin g electron microscopy was used to evaluate the resultant surface morph ology. Angle-resolved high-resolution photoemission measurements on th e valence band electronic structure and Cu 2p, in 3d, Ga 2p, and Se 3d core lines were used to evaluate the chemistry of the chemically trea ted surfaces. CdS overlayers were then deposited on these chemically t reated surfaces. Photoemission measurements were acquired to determine the resultant heterojunction valence-band discontinuity between the C dS and the chemically modified CuInSe2 surface. (C) 1997 American Vacu um Society.