Modelling hydrogen in the group-III nitrides by its pseudo-isotope, muonium

Abstract

Muon and muonium states in the wide-bandgap semiconductors BN, AlN, and GaN are characterised by various types of μSR measurement on polycrystalline samples. The muonium fractions range from 80% in hexagonal BN to zero in GaN. The hyperfine constants estimated from repolarization curves are 80% of the free muonium value in BN and 95% in AlN, with superhyperfine interactions to the host nuclei is evident. The electronically diamagnetic states show strong level-crossing resonances in AlN and GaN (although none is detectable in BN). These have the signature of cross-relaxation to 14N in AlN and to 69Ga and 71Ga in GaN, suggesting that the diamagnetic states are Mu + and Mu − in these naturally p- and n-type materials, respectively. Mu − diffusion in GaN sets is only above 600 K, with an activation energy of 1 eV.