Muonium centers in GaAs and GaP

The authors present the first observation of muon spin rotation for normal (Mu) and anomalous (${\mathrm{Mu}}^{\mathrm{*}}$) muonium centers in compound semiconductors, specifically GaP and GaAs. As in the elemental semiconductors, the muonium defect centers are characterized by a large isotropic hyperfine interaction for Mu but by a small, highly anisotropic, 〈111〉 symmetric hyperfine interaction for ${\mathrm{Mu}}^{\mathrm{*}}$. All hyperfine parameters measured in GaAs are remarkably close to those obtained in GaP. Furthermore, ‖$A_{\mathrm{para}}^{\mathrm{*}}$‖ is greater than ‖$A_{\perp }^{\mathrm{*}}$‖ for ${\mathrm{Mu}}^{\mathrm{*}}$. These last results are in marked contrast with the observations in diamond, Si, and Ge.