VALENCE-SUBBAND LEVEL-CROSSING IN GAAS GAASP STRAINED-BARRIER QUANTUM-WELL STRUCTURES OBSERVED BY CIRCULARLY-POLARIZED PHOTOLUMINESCENCE EXCITATION SPECTROSCOPY/

We have investigated the level configuration of the valence subbands i n GaAs/GaAs1-xPx (x = 0.23) strained-barrier quantum well structures a s a function of the well width. Circularly polarized photoluminescence excitation (CPPLE) spectroscopy was used to identify the heavy- or li ght-hole character of the optical transitions. Distinct polarization p roperties were observed in the strain-split heavy-and light-hole bands in the GaAsP barriers, which indicates the photoexcited electrons in the barriers retain spin orientation well even after the capture into the well and the relaxation process. Utilizing this polarization tende ncy of the transitions in the barriers, we could distinguish unequivoc ally the heavy- and light-hole character of the quantum well-related t ransitions. By varying the well width systematically, we observed the level crossing between n = 1 heavy- and light-hole transitions around the well width of 4 nm. This is in good agreement with the calculation based on the effective mass approximation.