Muonium as a Shallow Center in GaN

金沢大学理学部The observation of a paramagnetic muonium (Mu) spectrum in single-crystalline gallium nitride (GaN) was discussed. It was observed that a paramagnetic muonium center with extremely small hyperfine parameter was formed in GaN below 25 K. The small hyperfine parameter and small ionization energy of the Mu state indicated that muonium in one of its sites produced a shallow state, which raised the possibility that the analogous hydrogen center was a source of n-type conductivity in GaN. It was also observed that the Mu state had a high anisotropic hyperfine structure with axial symmetry along the [0001] direction, which indicated that the state was located either at a nitrogen-antibonding or a bond-centered site oriented parallel to the c axis