Location of the hydrogen donor in InN: evidence from muonium results

Muon spin depolarization measurements in a zero applied magnetic field confirm the existence of a shallow muonium (Mu) donor in InN, consistent with earlier transverse-field muon spin precession results. The zero-field data imply two Mu⁺ centres in InN, similar to those associated with channel and cage sites in GaN. The zero-field results provide strong evidence that the shallow Mu⁰ ionizes to Mu⁺ at its lowest-energy location. We argue that data on Mu in the III–V nitrides, taken in total, support the assignment of a wurtzite channel location to the shallow hydrogen donor in InN. The present results yield 15.4 ± 2 meV below the conduction band edge for the donor level depth.