EXPERIMENTAL-STUDY OF THE GAMMA-X ELECTRON-TRANSFER IN TYPE-II (AL,GA)AS/ALAS SUPERLATTICES AND MULTIPLE-QUANTUM-WELL STRUCTURES

A detailed experimental study of the real-space -X transfer in type-II GaAs/AlAs short-period superlattices and in type-II AlxGa1-xAs/AlAs multiple-quantum-well structures is presented. Transfer times on a subpicosecond and picosecond time scale are observed. The time constants critically depend on the thickness of the (Al,Ga)As layers, but not on the AlAs-layer thickness in the samples studied. The -X transfer rate is determined by the spatial overlap of the and X wave functions confined in the different layers. Intensity- and temperature-dependent measurements provide insight into the scattering mechanism. We conclude that electron LO-phonon scattering is the dominant scattering process for samples with thick (Al,Ga)As layers (>100). In contrast, interface scattering due to the interface mixing potential (-Xz mixing) and/or due to potential fluctuations caused by interface roughness (-Xx,y mixing) probably dominates for samples with thin (Al,Ga)As layers (<35). © 1990 The American Physical Society.