Resonant hole localization and anomalous optical bowing in InGaN alloys

Using large supercell empirical pseudopotential calculations, we show that alloying of GaN with In induces localization in the hole wave function, res onating within the valence band. This occurs even with perfectly homogeneou s In distribution (i.e., no clustering). This unusual effect can explain si multaneously exciton localization and a large, composition-dependent band g ap bowing coefficient in InGaN alloys. This is in contrast to conventional alloys such as InGaAs that show a small and nearly composition-independent bowing coefficient. We further predict that (i) the hole wave function loca lization dramatically affects the photoluminescence intensity in InGaN allo ys and (ii) the optical properties of InGaN alloys depend strongly on the m icroscopic arrangement of In atoms. (C) 1999 American Institute of Physics. [S0003-6951(99)00613-0].