Non-uniform tunneling transport in composite InGaAs/AlGaAs and GaAs/AlGaAs multiple quantum wells

摘要

The vertical tunneling transport of selectively and resonantly photogenerated carriers in a composite quantum-well system, consisting of dual multiple-quantum-wells (MQWs) with different heterostructures, i.e., GaAs/AlGaAs (MQW1) and strained InGaAs/AlGaAs (MQW2), is experimentally investigated at 15 K as a function of electric field by photocurrent (PC) response and photoluminescence (PL) measurements. In PC spectra of this novel structure, distinct pseudo-negative peaks are observed at the exciton resonance wavelengths of the front MQW1. Origins of the pseudo-negative PC peaks are explained by shadowing effects on the number of photons absorbed in the MQW1 layer and by assuming the dominance of electron transport. In the PC spectra, however, the excitonic peaks of the rear MQW2 shift to the lower energy side with increasing the electric field, while no significant shifts are observed for the negative PC peaks of MQW1. In addition, the applied reverse bias dependence of the PL intensities indicates faster decreases for the MQW2 layer, while the strong PL intensity persists at much higher fields for the MQW1 layer. These results clearly indicate that selective carrier injection into the MQW layers causes a non-uniform distribution of the applied electric field, which is useful to realize the charge-induced optical switching between the two MQW layers.