Quantum diffusion of muonium in GaAs with shallow donor impurities

Muonium diffusion was studied in silicon doped GaAs by means of muon spin relaxation in a longitudinal field. The muonium hopping frequencies in two samples with n-type carrier concentration of 1012∼14 cm−3 and 8×1016 cm−3 were deduced by using the model of fluctuating effective local fields. We found that muonium diffusion is strongly influenced by the dilute Si impurity in both samples in the temperature range belowTΔ≃30K. The absence of such a behavior in compensated high-resistivity samples indicates that the presence of shallow donor levels plays a decisive role for the tunneling diffusion of muonium in semiconductors.