Electronic structure of anomalous muonium in GaP and GaAs

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Abstract
The nuclear hyperfine structure of anomalous muonium in GaP has been resolved using muon level-crossing resonance. We find that 43% of the unpaired electron spin density resides on the nearest-neighbor Ga and 35% on the nearest-neighbor P on the 〈111〉 axis of symmetry. The s and p character of the unpaired spin density indicates that the Ga and P are displaced 0.23 and 0.54 Å away from the bond center. The now complete set of measured muon and nearest-neighbor nuclear hyperfine parameters for anomalous muonium in GaP and GaAs allows a detailed comparison of the two compounds, showing that the distribution of spin density among the group-III and group-V nearest neighbors in GaP is almost exactly the opposite of that in GaAs. This is contrary to what one would expect from a simple model of anomalous muonium in compound semiconductors involving an account of bonding characteristics.