Abstract

We report on the photoluminescence in quantum wells that have a low-density (n_e < 2 × 10¹⁰ cm⁻²) two-dimensional electron gas (2DEG). Mixed type I–type II GaAs/AlAs quantum wells are studied in which the 2DEG is photogenerated in the type I quantum wells and n_e is determined by the excitation intensity. The photoluminescence spectrum at T = 2 K is dominated by the recombination of a complex consisting of an electron bound to an exciton (a trion). It has a Lorentzian line shape whose width increases with increasing n_e. This dependence is attributed to trion–electron scattering processes. We present a model of the elastic trion–electron scattering and calculate its rate as a function of n_e. The model is based on a pair Coulomb interaction, and we fit the trion linewidth dependence on n_e by using the 2DEG screening wave vector (q_s) as a free parameter. The intensity at the low-energy tail of the trion band increases with n_e, and we attribute it to inelastic trion–electron scattering processes.

© 1996 Optical Society of America

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