FIELD-DEPENDENT VERTICAL-TRANSPORT STUDIES IN AL0.24GA0.76AS GAAS DOUBLE-QUANTUM-WELL STRUCTURES/

We report on temperature and electric field dependent photoluminescenc e (PL) and photoluminescence excitation (PLE) investigations on asymme tric double-quantum-well (ADQW) structures. Each sample contains AlGaA s/GaAs QWs, 3 nm and 6 nm wide, separated by an AlGaAs barrier with va rying width, and AlAs cladding barriers on both sides of the ADQW stru cture. The temperature dependent PL and PLE spectra demonstrate a vert ical carrier transport between the wells across the AlGaAs barrier. Th is process can be contolled by application of an external electric vol tage, resulting in an opposite change of the two QW PL intensities. Th e vertical transport was also studied by recording both PL and PLE spe ctra while modulating: the external field. This allows study of the in fluence of temperature, excitation wavelength, and both sign and magni tude of the external field in more detail. For high fields the vertica l carrier transport is dominated by holes. This result is explained us ing simple rate equation considerations.