Hydrogen in GaN
Hydrogen is implicated in the low doping efficiency of acceptors (e.g., Mg) in MOCVD-grown GaN by the following observations: the well-established role of hydrogen in the same phenomenon in other semiconductors; re-passivation of thermally activated Mg in GaN upon exposure to NH3 or H at temperatures > 400°C; correlation between Mg and H concentrations; and computational studies on the diffusivities of charged H in GaN and on the configuration and stability of the Mg-H complex in GaN. Strong experimental evidence for the Mg-H complex comes from variable-temperature Hall effect measurements which reveal that after hydrogenation of activated GaN:Mg the hole mobility increases as the hole concentration decreases, which is consistent with removal of ionized scattering centers and not with the introduction of separate compensating defects. However, experimental evidence is also accumulating to suggest that the Mg activation process involves the generation or transformation of electrically active defects.
Johnson, N. M. ; Goetz, W . Hydrogen in GaN. Gallium Nitride and Related Materials - Proceedings of the First International Symposium, edited by R.D. Dupuis, J.A. Edmond, S. Nakamura, and F.A. Ponce, held at the MRS Fall Meeting; 1995 November 27-December 1; Boston, MA. Warrendale, PA: Materials Research Society; 1996; 395: 723-732.