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-theory calculations. Stacking-fault energies are found to be largest for AlN and smallest for GaN consistent with density-functional results for the wurtzite/zinc-blende energy differences. Estimates are also given for stacking-fault energies in the zinc-blende structure. The values are negative, consistent with observations that nominal zinc-blende films typically contain large numbers of stacking faults. A related result is that hexagonal structures with stacking sequences repeating after four and six bilayers have lower energies than zinc-blende for all three compounds.