Photoluminescence from excitons at the mini‐Brillouin‐zone boundary in a GaAs/AlAs superlattice

Abstract

AbstractWe have investigated the photoluminescence (PL) properties related to the mini‐Brillouin‐zone boundary (π point) in a (GaAs)24/(AlAs)2 superlattice. In order to detect the PL from the π‐point exciton that has a very fast relaxation process in momentum space, we measured time‐resolved PL (TRPL) spectra with a streak‐camera system. Photoreflectance spectroscopy was adopted to characterize the optical transition energies at the mini‐Brillouin‐zone center (Γ point) and the π point, which results in the clear observation of the heavy‐hole‐exciton transition in the first quantization (n = 1) miniband at the π point, H11(π), in addition to the Γ‐point exciton, H11(Γ) usually observable. We have found that PL band relevant to the H11(π) transition appears in the TRPL spectra by tuning the excitation energy to the H11(Γ) transition. Furthermore, the H11(π)‐PL band has a delay time relative to the H11(Γ)‐PL band, which reflects the pileup of excitons and carriers from the Γ point to the π point in the miniband dispersion. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)