Fatigue and Recovery Effects of the 0.65-eV Emission Band in GaAs

The photoluminescence fatigue effect is carefully reinvestigated on a typical emission with a broad peak around 0.65 eV, believed to be associated with the main deep donor EL2, in undoped Czochralski-grown GaAs crystals. A characteristic recovery effect is found to occur in the “fatigued” emission band by continuous irradiation with Ar laser (514.5 nm); this is explained as an optical transition from the metastable state of the EL2 level to the conduction band in the configuration coordinate diagram. A wide variety of fatigue and recovery rates indicates that various lattice relaxations are induced by the microdefects responsible for the EL2 level.