Frequency Shift with Temperature as Evidence for Donor-Acceptor Pair Recombination in Relatively Puren-Type GaAs

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Abstract
Photoluminescence spectra of relatively pure GaAs display four emission bands at low temperatures, with energies near 1.51, 1.49, 1.455, and 1.42 eV. We report evidence that the 1.49-, 1.45-, and 1.42-eV bands are, respectively, a donor-acceptor recombination band, as suggested by Gershenzon, and two weaker replicas displaced by one and two phonons. With increasing temperature in the range from 25 to 35°K, the 1.49-eV band shifts slightly toward higher energy and is quenched in favor of the 1.51-eV band, while the total emission remains constant. The two lower energy bands change in frequency and intensity in exactly the same manner as the 1.49-eV band. We interpret the shift toward higher energy as due to an increasing importance of recombination of more closely spaced donor-acceptor pairs, and the quenching of the recombination band as due to increasing ionization of the donors. In addition, slight variations of the properties of the 1.49-eV band with increasing excitation intensity were noted which are compatible with the donor-acceptor recombination hypothesis.