Composition dependence of photoluminescence of Al<i>x</i>Ga1−<i>x</i>As grown by molecular beam epitaxy

Abstract

Low-temperature (∼4 K) photoluminescence of lightly Si-doped AlxGa1−xAs grown by molecular beam epitaxy has been studied. The defect-related emissions, due to the defect exciton (d, X) and the defect complex (d), have been identified. The peak energies of these emissions, which are 1.505 eV (d, X) and 1.474 eV (d) for GaAs, have been determined as a function of the mole fraction x ( x&amp;lt;0.45). The energy difference between the donor–bound-exciton (BE) peak and the defect-exciton peak is almost constant (∼9 meV). In contrast, the energy difference of the BE peak and the defect-complex peak increases from 40 meV at x=0 to about 70 meV at x∼0.4. In addition, the ionization energies of carbon and silicon acceptors in AlxGa1−xAs have been determined as a function of x and compared with theoretical calculations.