Lawrence Berkeley National Laboratory

We present a first principle investigation of the electronic structure and the band gap bowing parameter of zinc-blende \AlGaN using both local density approximation and screened-exchange density functional method. The calculated sX-LDA band gaps for GaN and AlN are 95 percent and 90 percent of the experimentally observed values, respectively, while LDA under estimates the gaps to 62 percent and 70 percent. In contrast to the gap itself, the band gap bowing parameter is found to be very similar in sX-LDA and LDA. Because of the difference in the conduction band structure, the direct to indirect band gap crossover is predicted to occur at different Al concentration.