Symmetry of metastable EL2 luminescence centres in semi-insulating GaAs single crystals

The method of polarised luminescence was used to prove optical anisotropy and to determine the symmetry of the two defects from the EL2 family which are responsible for the photoluminescence bands at 0.64 and 0.59 eV. The symmetry groups of these centres were established to be not higher than C2v and C3v, respectively. Orientations of the absorbing and emitting optical dipoles and types of dipole transitions were determined for each centre.