OPTICAL AND STRUCTURAL-PROPERTIES OF III-V NITRIDES UNDER PRESSURE

Self-consistent linear muffin-tin-orbital band-structure calculations are used to investigate the optical and structural properties of III-V semiconducting nitrides under hydrostatic pressure. The pressure behavior of the energy band structures is discussed in the context of the postulated chemical trends in III-V semiconductors. The regions in k space of dominant interband contributions to the elements of structure in the dielectric functions are identified. The total-energy calculations suggest that all the nitrides under pressure transform to the semiconducting rocksalt phase. The calculated transition pressures are 21.6 GPa (InN), 51.8 GPa (GaN), 16.6 GPa (A1N), and 850 GPa (BN). Experimental values that agree well with this have been found for the first three compounds. The fact that GaN and A1N have such different transition pressures in spite of their very similar ionicities is explained by the presence of 3d states on Ga.