Optical time-of-flight measurement of carrier transport in GaAs/AlxGa1−xAs and In0.53Ga0.47As/In0.52Al0.48As multiquantum wells

Abstract

An all‐optical time‐of‐flight technique is used for measuring perpendicular carrier transport in semiconductor heterostructures and multiquantum wells (MQWs). This technique is based on measuring a change in surface reflectance due to the absorption nonlinearities induced by the carriers, and has a temporal resolution of ∼1 ps. Typical results on a GaAs/Al_xGa_1−xAs MQW and an In_0.53Ga_0.47As/In_0.52Al_0.48As MQW are compared. The observed fast transport times can only be explained by a field‐dependent carrier emission out of the quantum well, after which transport through the continuum states can occur. Due to larger barriers in the In_0.53Ga_0.47As/In_0.52Al_0.48As system, this intrinsic limit to transport is much larger, and hence these devices are observed to be slower than their GaAs/Al_xGa_1−xAs counterparts.