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-phas e epitaxy growth process using DEALO [(C2H5)2AlOC2H5] as the oxygen so urce has been characterized by temperature-dependent (12-300 K) photol uminescence. Oxygen-related deep level photoluminescence bands were de tected at approximately 0.8 and approximately 1.1 eV. The relative int ensities of the two bands were sensitive to both oxygen concentration and temperature. At a given temperature, an increase in oxygen concent ration led to an increase in the intensity of the lower energy band re lative to the higher energy band. A similar effect occurred at a given oxygen concentration as the temperature was raised. Band edge lumines cence was also measured and was observed to quench when the oxygen con centration exceeded approximately 10(18) cm-3. The results indicate th at oxygen is incorporated differently in epitaxial GaAs than in bulk G aAs. 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 equal ly plausible microscopic models, based on the number of nearest-neighb or Al associated with O and multiple charge states, to explain the pro perties of the oxygen-related photoluminescence.