Vertical transport of electrons and holes in short period GaAs---AlGaAs superlattices

Owing to the use of a high sensitivity streak camera we are able to observe photoluminescence (PL) decays with excitation density as low as 10¹⁴ photocarriers cm⁻³ per pulse. At such low densities photoexcited electrons are the minoritar carriers in our residual p-type MBE materials and they move freely. By varying the excitation density we are able to evidence the transition from electron transport regime to ambipolar motion. We have studied a series of samples superlattices (SLs) of different periods and AlGaAs reference alloy with an enlarged well (EW) located at about 1 μm from the surface. The vertical transport in these structures is analysed by measuring the dynamics of the photoluminescence.