Spatially direct and indirect photoluminescence from InAs/AlSb heterostructures

Abstract

We present a Fourier-transform photoluminescence study of InAs/AlSb type-II heterostructures, spanning the midinfrared 1--12-\ensuremath{\mu}m wavelength range. The investigated samples consist of single and double quantum wells, grown on GaAs substrates by molecular-beam epitaxy, with different buffer-layer structures for strain accommodation. The photoluminescence intensity is found to be very sensitive to the detailed structure of the underlying buffer sequence. The use of a GaSb buffer or a GaSb/AlSb superlattice in the buffer gives rise to an additional radiative-recombination channel in the near infrared, which competes with radiative recombination in the InAs quantum wells at longer wavelengths. Variations in the spectra observed under visible and infrared excitation provide evidence that the recently observed persistent photo effect is governed by hole capture in the GaSb layers in the buffer sequence. Furthermore, very wide quantum wells (100 and 200 nm) show spatially direct as well as spatially indirect photoluminescence, providing insight into the nature of the transition from the bulklike semiconductor to the type-II heterostructure.