Fermi level dependence of hydrogen diffusivity in GaN

Hydrogen diffusion studies were performed in GaN samples with different Fer mi level positions. It is shown that, at 350 degreesC, hydrogen diffusion i s quite fast in heavily Mg doped p-type material with the Fermi level close to E-v + 0.15 eV, considerably slower in high-resistivity p-GaN(Zn) with t he Fermi level E-v + 0.9 eV, while for conducting and semi-insulating n-GaN samples with the Fermi level in the upper half of the band gap no measurab le hydrogen diffusion could be detected. For these latter samples it is sho wn that higher diffusion temperature of 500 degreesC, and longer times (50 h) are necessary to incorporate hydrogen to appreciable depth. These findin gs are in line with previously published theoretical predictions of the dep endence of hydrogen interstitials formation in GaN on the Fermi level posit ion. (C) 2001 American Institute of Physics.