INTERVALLEY SCATTERING TIME IN TYPE-II ALXGA1-XAS/ALAS MULTIPLE-QUANTUM WELLS

Time-resolved photoluminescence (PL) experiments are reported on two AlxGa1-xAs/AlAS type-II multiple-quantum-well structures as a function of applied uniaxial stress parallel to the [110] direction, at T = 4.5 K. The AlAs layer thicknesses of both samples are such that the X(z) valley is higher in energy than the X(x) and X(y) valleys. By using a time-windowing technique, the PL from both X(z) and lower-lying X(x) and X(y) states could be observed simultaneously providing a direct measure of the energy separation (DELTAE) between the two valleys. With the application of a uniaxial stress, the time decay of the hot X(z) PL is then measured for various values of DELTAE, providing intervalley X(z) - X(x) and X(z) - X(y) scattering times in the AlAs layers. The various mechanisms responsible for this relaxation process are identified.