抄録
We have studied the optical properties of AlxGa1−xAs-AlAs ternary alloy multiquantum-well structures around two Γ−X crossovers by means of photoluminescence and absorption saturation. In the photoluminescence, the peak due to the n=1 heavy exciton (Γ−Γ) is observed for Al composition x from 0 up to 0.34. When x is 0.34 or more, another kind of the peak due to the Γ−X recombination (recombination between an X-electron in AlAs and a Γ-hole in AlxGa1−xAs) is observed in the low energy side, corresponding to the first Γ−X crossover. In the absorption saturation experiments, on the other hand, the saturation was observed in all the samples except the Al0.51Ga0.49As-AlAs sample corresponding to the second Γ−X crossover. The fact suggests that Γ-electrons relax to the X-state is the AlxGa1−xAs alloy very quickly compared with the other relaxation processes such as the Γ−Γ recombination in AlxGa1−xAs and the transfer of a Γ-electron in AlxGa1−xAs to X-state in AlAs.
