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

✍ Scribed by Gorczyca, I. ;Suski, T. ;Christensen, N. E. ;Svane, A.

• Book ID: 105366034
• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 209 KB
• Volume: 208
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.201000939

✦ Synopsis

Abstract

Using ab initio calculations a comparison between In~x~Ga~1−x~N, In~x~Al~1−x~N and Ga~x~Al~1−x~N is performed to examine the role of indium in nitride alloys. The band gap, E~g~, as well as its pressure coefficient, d__E__~g~/d__p__, are studied as functions of chemical composition, x. Following theoretical and experimental suggestions about the crucial role of In‐segregation in In~x~Ga~1−x~N and In~x~Al~1−x~N, different arrangements of In atoms, uniform and clustered are considered. The presence of In and its clustering introduces a significant reduction of both E~g~ and d__E__~g~/d__p__, as well as strong bowings. These effects are most pronounced in In~x~Al~1−x~N, (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.