Recent work on the properties of H defect centers in group-III nitrides, and relevant studies by µSR spectroscopy (muon spin rotation, relaxation and resonance) was reviewed; in particular, the results obtained via a form of nuclear quadrupole resonance. Implanted positive muons were used to mimic and model the behaviour of interstitial protons. The resultant defect centers exhibited both metastability and bistability. In AlN, they remained as positive ions but partitioned themselves between a highly mobile species and one that was trapped and immobilized at temperatures as high as 800K in cage-like sites adjacent to N. The barrier to escape from the cage was 0.86eV. In n-type GaN, the cage-site positive ions were stable only up to 200K. Above this temperature, they captured electrons to convert to negatively charged centers; the analogues of hydride ions, which relocated to sites antibonding to Ga. The latter escaped from the cage sites at around 600K, with an activation energy of 1.5eV, to join more mobile negative ions which diffused via channel sites with an activation energy of 0.65eV. Data on the neutral paramagnetic center suggested that H could act as a shallow donor in at least one other member of this family; that is, InN.

Hydrogen in Group-III Nitrides, Studied by Muon Spin Resonance. S.F.J.Cox, R.L.Lichti, E.A.Davis: Journal of Physics D, 2002, 35[7], 586-90