Abstract

We discuss 100-fsec, short-period (~120 nm) laser-induced transient grating techniques and their application to study perpendicular transport phenomena over nm-dimensions in GaAs/Al_0.3Ga_0.7As quantum-confined heterostructures. Our high temporal resolution has allowed us to directly resolve the transport even for superlattice samples with barriers as thin as 14 Å. By systematically varying the barrier width from 14 Å upwards, we have examined the transition from dominance of tunneling via the confined sub-levels to that of over-barrier hopping. We show that the extracted transport parameters are consistent with a simple rate-equation model of these processes. In addition to improved (100-fsec) resolution, these studies are to be contrasted to previous work on perpendicular transport using time-resolved photoluminescence¹ in that we report measurements taken at room temperature.

© 1990 Optical Society of America