Reconstructions on AlN Polar Surfaces under Hydrogen Rich Conditions

Structures and stability of AlN(0001) and (0001̄) surfaces under hydrogen rich conditions are theoretically investigated by performing first-principles pseudopotential calculations. The calculated surface energies demonstrate that several hydrogen incorporated structures are stabilized depending on the chemical potentials of constituting elements. Using surface phase diagrams, which are obtained by comparing the calculated adsorption energy with vapor-phase chemical potentials, we find that H atoms tend to desorb from AlN(0001) surface even under high H 2 pressures. In contrast, N–H bonds on AlN(0001̄) surface are found to be favorable over the wide range growth conditions. These results imply that the growth processes on AlN(0001) surface could be changed by growth conditions such as temperatures and pressures.