We report deep-center photoluminescence of GaAs grown at low temperatures between 200 and 400 ^∘{}C by molecular-beam epitaxy. Changes of temperature and excitation intensity were used in addition to heat-treatment and photoluminescence-excitation measurements. The type of photoluminescence transition strongly depends on the growth temperature and the [As₄]/[Ga] ratio. The layers grown at 200--300 ^∘{}C show a dominant emission at 0.68 eV (EL2) and an emission at 1.1 eV related to a VGa center. The layers grown at 325--400 ^∘{}C show one transition at 0.75--0.81 eV (designated as the 0.8-eV emission). We attribute the 0.8-eV emission to the Asᵢ-VGa center. The center shows the large lattice relaxation exemplified by the Franck-Condon shift of 0.34 eV. The thermal ionization energy is determined to be 0.36 eV. We discuss our assignment of the Asᵢ-VGa center to the well-known EL6 center.
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Yu et al. (1994) studied this question.