Publications

The authors have performed first-principles calculations to examine the effects of biaxial strain and chemical ordering on the band gap of wurtzite In{sub x}Ga{sub 1{minus}x}N in the range 0 {le} x {le} 0.5. The results for unstrained, random alloys are in good agreement with theoretical estimates and measurements on unstrained zinc-blende alloys, but are in poor agreement with recent measurements on strained wurtzite alloys which display significantly lower gaps. Biaxial strain is found to have a non-linear effect on calculated alloy gaps, increasing them for x < 0.25 and decreasing them for x > 0.25. However, the overall agreement with measured wurtzite values remains poor. Chemical ordering along the [0001] direction in strained alloys is found to decrease the band gaps considerably, yielding much improved agreement with measurements. They discuss their results with regard to current theories concerning the optical properties of wurtzite InGaN alloys.