Photoinduced Space-Charge Buildup by Asymmetric Electron and Hole Tunneling in Coupled Quantum Wells

We demonstrate, by photoluminescence measurements, the excitation-dependent opposite charging of coupled ${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$As/InP single quantum wells. The formation of the dipole layer is associated with band bending lining up the electron levels in the wells. This novel effect is due to the very different tunneling rates of electrons and holes through the barrier and is observed for barrier widths $L_B=40\mathrm{}-100$ Å. On the basis of these findings we discuss a potential new optical bistability.