Photocurrent Calculation of Intersubband Transitions to Continuum-Localized States in GaAs/AlGaAs Multiquantum Wells for Mid-Infrared Photodetector

In this paper, we propose a system based on GaAs heterostructure where it is possible to generate photocurrent with mid-infrared radiation. This system is based on a central quantum well (CQW) embedded in a superlattice. Because of the CQW, which acts as a defect, there are localized states between the mini-bands in the continuum of the conduction band. Unlike the usual systems where the final states are delocalized, the oscillator strength due to the transitions between electrons occupying the ground-state to these continuum-localized states is enhanced. An applied electrical bias mixes the mini-band states with the localized state in the continuum, and due to the combined effects of strong oscillator strength and high transmission coefficients, narrow and sharp peaks are observed in the photocurrent when exciting these final states. We calculate and present results of the absorption and photocurrent for a system built to operate at 4.1 μm and discuss their dependence with the bias applied to the system and with the intensity of the incident radiation.