Abstract

Excitonic spectra in superlattices with coupled wells are substantially modified by their subband-dispersion. For those excitons with their transition energies above the first quantized state, their spectra can be further complicated due to the mixing of the valence subbands. For example, mixing between n = 2 heavy-hole states and n–1 light-hole states can lead to triplet-like excitonic structures in coupled-well superlattices within a certain range of barrier widths. We have systematically investigated the effect of subband-mixing on n > 1 exciton spectra in a series of GaAs/Al_xGa_1-xAs superlattices at 10 K using excitation spectroscopy. The sample parameters were determined by transmission electron microscopy. Drastic exciton lineshape changes have been observed among different quantum number states in one sample, as well as among different barrier-width samples for the same quantum states. We will compare these data with theory. We will also present an empirical way of estimating the subband widths without going through complicated calculations.

© 1990 Optical Society of America