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The plane-wave pseudopotential (PWPP) method has been used to calculate structural and electronic properties of wurtzite and zinc-blende GaN. In contrast to previous studies using the PWPP method, the gallium 3d electrons were treated as valence electrons. This yields larger lattice constants and smaller energy gaps as compared with previous PWPP results. For wurtzite, the three structure parameters were found to be a =3.162 A, c =5.142 A, and u =0.377. For zinc blende, the cubic lattice constant 0 was found to be a0=4.460 A. The lattice constants are about 1' smaller than measured values and the cubic lattice constant is within about 0.2%%uo of results from full-potential all-electron calculations. This study demonstrates that it is both possible and practical to treat gallium 3d electrons explicitly using the PWPP method.

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First-principles calculations have been used to determine bowing parameters for disordered zinc-blende Al1−xGaxN and Ga1−xInxN. The direct transition at Γ is found to bow downward for both materials with parameters +0.53 and +1.02 eV, respectively, while the Γ-to-X transition bows upward for Al1−xGaxN (parameter −0.10 eV) and downward for Ga1−xInxN (parameter +0.38 eV). The similarity of the calculated bulk zinc-blende and wurtzite Γ-point transitions also allows estimates to be made of the energy gap versus composition for wurtzite alloys.