Isotope effects on the rate of electron-beam dissociation of Mg-H complexes in GaN

The effect of low-energy electron-beam irradiation on the stability of acceptor-hydrogen complexes in Mg-doped GaN has been directly examined with infrared optical spectroscopy. Consistent with prior electrical transport data, we find that Mg-H pairs begin to break apart under 25 keV electron-beam exposure at doses of a few mC/cm2. However, we find that, even after long exposures, roughly 12 of the acceptor-hydrogen pairs remain unaffected by the electron exposure. Using Mg-doped samples that have been vacuum annealed and D2 gas exposed, we demonstrate that there is a large (∼×5) isotopic shift in the beam-induced debonding rate of these acceptor-hydrogen complexes. H and D remain in the material during these treatments, and Mg-H or Mg-D reforms during postirradiation annealing. The implications of these observations for understanding the nature of the debonding process and the subsequent reactions of the detached H/D in the GaN lattice are discussed. © 2002 American Institute of Physics.