Energies for muonium defect levels in semiconductors

We have determined the ionization energies for Mu0Mu0 centers in several semiconductor materials to locate the thermodynamic donor and acceptor levels for muonium with respect to the conduction and valence band edges. For Si, Ge, GaAs, and GaP the bond-centered (BC) donor level lies above the T-site acceptor level, verifying the negative-U character of muonium impurities. The midpoint between the acceptor and donor levels lies at a common energy for these materials to within the experimental uncertainties when using the theoretical band alignments. Mu defect levels can be assigned for ZnSe and 6H–SiC which match this result. Experimental data for muonium are compared to existing experimental results and predictions for the analogous hydrogen defect centers.