Abstract

Reduction of the GaAs well width in (GaAs)_m/(AlAs)_n (m,n = number of monolayers) superlattices (SL) permits tuning of the lowest Γ-conduction band state in the GaAs above the X-minimum in the AlAs layers for m ≤12. In such a staggered type-II SL the highest valence band state is contained in the GaAs layers whereas the lowest conduction band state occurs in the AlAs slabs. After photoexcitation of hot electrons and holes in the confined Γ conduction- and valence-band states of the GaAs layers in a type- II SL, the holes stay in the GaAs slabs during relaxation. In contrast, the electrons scatter from the Γ-related states of the GaAs layers to the energetically lower X-related states of the AlAs layers.

© 1990 Optical Society of America