ELECTRONIC-STRUCTURE AND EQUILIBRIUM PROPERTIES OF GAXAL1-XN ALLOYS

First-principles calculations by means of the linear-muffin-tin-orbital method were carried out of the electronic band structures, equilibrium lattice constants, energies of formation, and bulk moduli of GaxAl1-N-x alloys in zinc-blende-derived structures with a specific cation ordering. The miscibility and band-gap bowing of disordered alloys were studied using a cluster expansion method. Complete mutual solubility is predicted to occur at typical growth temperatures. The band gap is found to exhibit a weak bowing and to change from being indirect (Gamma --> X) for x = O to direct at Gamma at a concentration of x approximate to 0.4.