Band gap bowings and anomalous pressure effects in III–V nitride alloys: Role of In‐segregation

Abstract

AbstractUsing ab initio calculations a comparison between InxGa1−xN, InxAl1−xN and GaxAl1−xN is performed to examine the role of indium in nitride alloys. The band gap, Eg, as well as its pressure coefficient, dEg/dp, are studied as functions of chemical composition, x. Following theoretical and experimental suggestions about the crucial role of In‐segregation in InxGa1−xN and InxAl1−xN, different arrangements of In atoms, uniform and clustered are considered. The presence of In and its clustering introduces a significant reduction of both Eg and dEg/dp, as well as strong bowings. These effects are most pronounced in InxAl1−xN, (with x = 0.25) and depend strongly on clustering geometry. It is shown that the In–N bonds are shortened when more than one In‐cation is bound to one nitrogen anion. The strong hybridization of wave functions (In‐p,d‐states and N‐p‐states) at the top of the valence band is responsible for the enhancements of bowings in the case of clustered distribution of indium atoms.