Abstract

GaAs-AlAs type-II quantum wells provide interesting media for investigation of the many- body effects associated with a one-component plasma.^1-6When the GaAs layer thickness is less than 35 Å and the AlAs layer thickness is greater than 16 Å, the lowest Γ-electron state of the GaAs well lies energetically above the X minimum of the AlAs barrier, whereas the lowest-energy hole state remains in the GaAs layer (see inset of Fig. 1). As a result of such a band alignment, optical excitation of electron-hole pairs in the GaAs layer creates a spatial separation of the two-component plasma; electrons scatter from the Γ state in GaAs to the X state in AlAs. This allows measurement of the dynamics of the hole relaxation in the GaAs layer, in which they are spatially separated from the electrons in the AlAs layer. Here we report on such measurements at T = 10 K with 130-fs laser pulses tuned resonantly inside the heavy-hole exciton peak of a type II quantum-well structure consisting of ≅ 28-Å-thick GaAs layers (10 monolayers) and ≅ 57-Å-thick AlAs layers (20 monolayers).

© 1991 Optical Society of America