UNEXPECTED BAND-GAP COLLAPSE IN QUATERNARY ALLOYS AT THE GROUP-III-NITRIDE GAAS INTERFACE - GAALASN/

We present first-principles relativistic pseudopotential calculations of the structural and electronic properties of the quaternary alloy Ga AlAsN. We have found a surprising band-gap collapse, in contrast to th e empirical and first-principles virtual-crystal approximation (VCA) c alculations that predict a wide band gap. Unusually strong structural relaxation caused by large differences in the strength of the chemical bonds between the m-V ions in the alloy invalidates the VCA and leads to the band-gap collapse. These results have important implications f or other complex semiconductor alloys. [S0163-1829(98)00108-8].