BASAL-PLANE STACKING-FAULTS AND POLYMORPHISM IN ALN, GAN, AND INN

Energies of basal-plane stacking faults in wurtzite AlN, GaN, and InN are determined using a one-dimensional Ising-type model incorporating effective layer-layer interactions obtained from density-functional-th eory calculations. Stacking-fault energies are found to be largest for AIN and smallest for GaN consistent with density-functional results f or the wurtzite/zinc-blende energy differences. Estimates are also giv en for stacking-fault energies in the zinc-blende structure. The value s are negative, consistent with observations that nominal zinc-blende films typically contain large numbers of stacking faults. A related re sult is that hexagonal structures with stacking sequences repeating af ter four and six bilayers have lower energies than zinc-blende for all three compounds. (C) 1997 American Institute of Physics.