Direct-indirect band gap crossover in two-dimensional GaSb/AlSb-quantum-well-structures

Abstract Using excitation and time-resolved spectroscopy we have investigated the size-dependent change from direct to indirect band structure in two-dimensional GaSb/AlSb structures. In the indirect regime (L z ⩽38 A) we observe L- and Λ-point transitions, whereas in the direct-gap samples only the Λ-point emission occurs. Direct evidence for the crossover is provided by the increase of the carrier life-time from less than 1 ns in direct-gap samples to more than 100 ns in indirect-gap samples.