Influence of ambient on hydrogen release from p-type gallium nitride

Abstract

Mechanisms of H release from Mg-doped, p-type GaN were investigated in vacuum, in N2 and O2 gases, and in electron–cyclotron-resonance N2 plasmas. Replacing grown-in protium with deuterium (D) and employing sensitive nuclear-reaction analysis allowed the retained concentration to be followed quantitatively over two decades during isothermal heating, illuminating the kinetics of controlling processes. Oxidation attending the O2 exposures was monitored through nuclear-reaction analysis of O18. N2 gas at atmospheric pressure increases the rate of D release appreciably relative to vacuum. The acceleration produced by O2 gas is much greater, but is diminished in later stages of the release by oxidation. The N2 plasma employed in these studies had no resolvable effect. We argue that surface desorption is rate controlling in the D release, and that it occurs by D–D recombination and the formation of N–D and O–D species. Our results are quantitatively consistent with a theoretical model wherein the bulk solution is in equilibrium with surface states from which desorption occurs by processes that are both first and second order in surface coverage.