Role of hydrogen in surface reconstructions and growth of GaN

We present first-principles calculations for the atomic structure and energetics of hydrogenated GaN(0001) surfaces. The geometry of the most relevant surface reconstructions is discussed in detail. Finite-temperature effects are included through calculations of the Gibbs free energy and the stability of various surface reconstructions is analyzed in terms of a generalized surface phase diagram. A comparison with recent experiments elucidates the energetic and structural properties of GaN surfaces under growth conditions. (C) 2002 American Vacuum Society.