Interlayer charge transfer in n-modulation doped Al_(1-x)Ga_xAs-GaAs single heterostructures

摘要

We studied the interlayer charge transfer in n-modulation doped Al1-xGaxAs-GaAs single heterostructures by photoluminescence and magnetotransport. Photoluminescence contributions from a high-mobility quasi-twodimensional electron system at the interface and GaAs bulk type excitons were analyzed, covering an excitation intensity range of nearly three orders of magnitude. The experiment was compared with selfconsistent band structure calculations that allowed to follow the charge redistribution in the sample. After sample cool down in the dark a parallel conducting quasi-twodimensional channel of low electron mobility appeared in the Al1-xGaxAs-layer, that gained in density up to a saturation value. There was only little interaction between the Al1-xGaxAs and GaAs sides in the persistent regime and a reduction of the depletion charge in the GaAs could largely account for the interface channel density enhancement. Contrary, the negative photoeffect present during continuous illumination strongly depends on the interaction between the interface and the parallel channel, which serves as a temporary sink for excess charges from the GaAs side. When the illumination is switched off the parallel channel acts as a source and the sample essentially returns to the prior illumination state of saturation.