Recent muon spin-precession experiments confirmed that muonium, a light H isotope, forms a shallow donor in InN. Depolarization measurements in zero-magnetic field were in agreement and show more than one positively charged center. Below 350K, one Mu+ signal had a depolarization function typical of a static center, while a second relaxes more weakly with the characteristics of slow tunneling motion. In combination, spin precession and zero-field data show conclusively that the shallow Mu0 ionizes to the Mu+ ground state. The static signal converts to that for the mobile state in two steps, suggesting two metastable Mu+ trap sites. Preliminary energies were extracted for the de-trapping transitions and thermally activated Mu+ diffusion.

Muonium (Hydrogen) Defect Centers in Indium Nitride. Y.G.Celebi, S.F.J.Cox, E.A.Davis, R.L.Lichti: Physica B, 2003, 340-342, 385-8