AN AB-INITIO PSEUDOPOTENTIAL CALCULATION OF GROUND-STATE AND EXCITED-STATE PROPERTIES OF GALLIUM NITRIDE

In this work, the electronic, ground-state and vibrational properties of both alpha-GaN (i.e. wurtzite structure) and the recently fabricate d beta-GaN (i.e. zincblende structure) have been studied using the ab initio pseudopotential method within the local density approximation a nd a simple quasi-particle scheme. The calculated equilibrium lattice constants, bulk moduli, the pressure derivatives of the bulk moduli, a nd the A1 TO(GAMMA) phonon frequency are in good agreement with availa ble experimental and other recent ab initio theoretical results. The s elf-energy band gap corrections are found to be highly kappa-dependent . The calculated fundamental band gap is direct in both cases and for the experimental lattice constant is calculated to be 3.36 eV in beta- GaN and 3.48 eV in alpha-GaN, in excellent agreement with experiment.