Field dependent vertical-transport studies in Al0.24Ga0.76AsGaAs double-quantum-well structures

We report on temperature and electric field dependent photoluminescence (PL) and photoluminescence excitation (PLE) investigations on asymmetry double-quantum-well (ADQW) structures. Each sample contains AlGaAsGaAs QWs, 3 nm and 6 nm wide, separated by an AlGaAs barrier with varying width, and AlAs cladding barriers on both sides of the ADQW structure. The temperature dependent PL and PLE spectra demonstrate a vertical carrier transport between the wells across the AlGaAs barrier. This process can be controlled by application of an external electric voltage, resulting in an opposite change of the two QW PL intensities. The vertical transport was also studied by recording both PL and PLE spectra while modulating the external field. This allows study of the influence of temperature, excitation wavelength, and both sign and magnitude of the external field in more detail. For high fields the vertical carrier transport is dominated by holes. This result is explained using simple rate equation considerations.