Orientation effect on intersubband tunneling of quantum wells grown on high-index GaAs(n11)A (n <= 4) substrates

The effect of the orientation on intersubband tunneling process in Al0.35Ga 0.65As/GaAs asymmetric double quantum wells (ADQWs) grown on GaAs(n11)A (n less than or equal to 4) substrates was studied by cw photoluminescence (PL ), time-resolved photoluminescence (TRPL) at low temperatures and transmiss ion electron microscope (TEM) measurements. The red-shift of two PL peaks f rom the wide quantum well (WW) and the narrow quantum well (NW) for substra te orientation far from the (100) plane is attributed to the large anisotro py of the heavy-hole band in the different GaAs orientations. TRPL experime ntal results show the decay time tau of the excitation from the NW is about 100 ps for (111)A and (211)A samples, which is 50% smaller than that of th e other samples. This fast tunneling process may be understood such that th e large anisotropy of the heavy-hole band for (111)A and (211)A planes caus es the resonant tunneling of holes between the WW and NW. The optical trans ition dependence of the orientation in ADQWs provides a useful method to es timate the tunneling time of holes through a barrier. (C) 2000 Elsevier Sci ence B.V. All rights reserved.