Optical Transitions of the Mg Acceptor in GaN

We report on the optical transitions of the neutral, paramagnetic Mg acceptor in GaN. Its identification is based on the magnetic circular dichroism of the absorption combined with optically detected magnetic resonance (ODMR). Close to the band-gap energy, the transition from the Mg0 ground state to the neutral-acceptor-bound exciton state (A0X) is observed. In addition, the hole-ionisation transition Mg0+hν→Mg-+h is detected in the infrared spectral range. The g-values and the anisotropy of the Mn acceptors agree with those derived by luminescence-detected ODMR.