THE EFFECTS OF TEMPERATURE AND OXYGEN CONCENTRATION ON THE PHOTOLUMINESCENCE OF EPITAXIAL METALORGANIC VAPOR-PHASE EPITAXY GAASO

Semi-insulating epitaxial GaAs:O prepared in a metalorganic vapor-phase epitaxy growth process using DEALO [(C2H5)2AlOC2H5] as the oxygen source has been characterized by temperature-dependent (12-300 K) photoluminescence. Oxygen-related deep level photoluminescence bands were detected at approximately 0.8 and approximately 1.1 eV. The relative intensities of the two bands were sensitive to both oxygen concentration and temperature. At a given temperature, an increase in oxygen concentration led to an increase in the intensity of the lower energy band relative to the higher energy band. A similar effect occurred at a given oxygen concentration as the temperature was raised. Band edge luminescence was also measured and was observed to quench when the oxygen concentration exceeded approximately 10(18) cm-3. The results indicate that oxygen is incorporated differently in epitaxial GaAs than in bulk GaAs. We propose that the difference is due to the incorporation of Al when DEALO is used in the growth of epitaxial GaAs:O. We suggest equally plausible microscopic models, based on the number of nearest-neighbor Al associated with O and multiple charge states, to explain the properties of the oxygen-related photoluminescence.