Defect-related emissions in photoluminescence spectra of AlxGa1−xAs grown by molecular beam epitaxy

We have studied defect-related emissions in low-temperature (∼4 K) photoluminescence of lightly Si-doped AlxGa1−xAs (x<0.45) grown by molecular beam epitaxy. The relative intensities of the defect exciton (d,X) and defect complex (d) emissions depend on the mole fraction x; the (d,X) emission becomes dominant for x>0.27. This suggests different origins for the (d,X) and (d) emissions. The (d,X) and (d) emissions are tentatively associated with oxygen and carbon, respectively.