Anti-Stokes photoluminescence between Inx(Al0.17Ga0.83)1−xAs/Al0.17Ga0.83As quantum wells with different x values

Anti-Stokes photoluminescence (AS-PL) has been investigated in a step-graded Inx(Al0.17Ga0.83)1−xAs/Al0.17Ga0.83As quantum well (QW) system consisting of five QWs with different x values. When a low-energy heavy-hole (1 s) exciton state in a particular well is resonantly photoexcited, the high-energy heavy-hole (1 s) exciton in the nearest-neighbor well shows a stronger AS-PL intensity than other QWs beyond the nearest-neighbor QW. The AS-PL intensity of (1 s) excitons observed in each well shows a drastic position dependence on the place where carriers are resonantly photoexcited, indicating energy transfer processes with a spatial position dependence. These results mean that the up-conversion phenomena responsible for generating high-energy carriers can be influenced by transfer and capture processes into the high-energy exciton state in addition to nonlinear excitation mechanisms.