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

Muon and muonium states in the wide-bandgap semiconductors BN, AlN, and GaN are characterised by various types of mu SR measurement on polycrystalline samples. The muonium fractions range from 80% in hexagonal BN to zero in G aN. The hyperfine constants estimated from repolarization curves are 80% of the free muonium value in BN and 95% in AlN, with superhyperfine interacti ons to the host nuclei is evident. The electronically diamagnetic states sh ow strong level-crossing resonances in AlN and GaN (although none is detect able in BN). These have the signature of cross-relaxation to N-14 in AlN an d to Ga-69 and Ga-71 in GaN, suggesting that the diamagnetic states are Mu( +) and Mu(-) these naturally p- and n-type materials, respectively. Mu(-) d iffusion in GaN sets is only above 600 K, with an activation energy of 1 eV . (C) 2000 Elsevier Science B.V. All rights reserved.