Analysis of phase-separation region in wurtzite group III nitride quaternary material system using modified valence force field model

The group III (B, Al, Ga, In) nitride quaternary alloy systems are potentia lly useful for ultraviolet, blue, and green light-emitting devices, or high -temperature, high-power, and high-frequency electronic devices. There have been significant challenges to the epitaxial growth of these alloys and we have investigated the unstable mixing region in the phase field. The exist ence of an unstable mixing region is predicted based on a strictly regular solution model. The interaction parameter used in our model is analytically obtained by the valence force field model modified for wurtzite structures . From our calculations, among the group III nitride quaternary alloy syste ms, we find that InGaAlN system has the narrowest unstable mixing region, a nd that the BInAlN system has the widest unstable mixing region. The calcul ated interaction parameters which are the important to predict the unstable mixing region agree well with the best-fit line of experimental results fo r various alloy systems. (C) 2001 Elsevier Science B.V. All rights reserved .