Orientation effect on intersubband tunneling of quantum wells grown on high-index GaAs n11/A nF4/ substrates

The effect of the orientation on intersubband tunneling process in Al0.35Ga0.65AsrGaAs asymmetric double quantum wells ADQWs.grown on GaAs n11.A nF4.substrates was studied by cw photoluminescence PL., time-resolved photoluminescence TRPL.at low temperatures and transmission electron microscope TEM.measurements. The red-shift of two PL peaks from the wide quantum well WW.and the narrow quantum well NW.for substrate orientation far from the 100. plane is attributed to the large anisotropy of the heavy-hole band in the different GaAs orientations. TRPL experimental results show the decay time t of the excitation from the NW is about 100 ps for 111.A and 211.A samples, which is 50% smaller than that of the other samples. This fast tunneling process may be understood such that the large anisotropy of the heavy-hole band for 111.A and 211.A planes causes the resonant tunneling of holes between the WW and NW. The optical transition dependence of the orientation in ADQWs provides a useful method to estimate the tunneling time of holes through a barrier. q2000 Elsevier Science B.V. All rights reserved.