Diffusion studies were made of samples having various Fermi-level positions. It was shown that, at 350C, H diffusion was quite rapid in heavily Mg-doped p-type material with a Fermi level close to Ev + 0.15eV. It was considerably slower in high-resistivity p-type GaN(Zn) with a Fermi level at Ev + 0.9eV. No measurable H diffusion could be detected in conducting and semi-insulating n-type GaN with a Fermi level in the upper half of the band-gap. The latter samples showed that a higher diffusion temperatures (500C) and longer times (50h) were required in order to incorporate H at appreciable depths. The results agreed with theoretical predictions of the dependence of H interstitial formation, in GaN, upon the Fermi-level position.

Fermi Level Dependence of Hydrogen Diffusivity In GaN. A.Y.Polyakov, N.B.Smirnov, S.J.Pearton, F.Ren, B.Theys, F.Jomard, Z.Teukam, V.A.Dmitriev, A.E.Nikolaev, A.S.Usikov, I.P.Nikitina: Applied Physics Letters, 2001, 79[12], 1834-6