Structural and electronic properties of chalcopyrite semiconductors AgXY2 (X = In, Ga; Y = S, Se, Te) under pressure

Results are presented of a first-principles calculation of the direct band-gap pressure coefficient a, for a series of Al, Ga and In chalcopyrite semiconductor compounds AgXY2 (X = Ga, In; Y = S, Se, Te) and the corresponding zinc-blende structure. Good agreement was found between the calculated and experimental pressure coefficients. It was found that a(g) in chalcopyrites are dramatically reduced relative to zinc-blende compounds, and that the Al --> Ga --> In substitution lowers ag in chalcopyrites more than in zinc-blende compounds. As a result, the empirical rule suggested for zinc-blende compounds, stating that for a given transition (e.g. Gamma(15v) --> Gamma(1c)) a(g) does not depend on substitutions, has to be modified for chalcopyrites. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.