Asymmetrically Doped GaAs/AlGaAs Double-Quantum-Well Structure for Voltage-Tunable Infrared Detection

We fabricate, characterize, and analyze tunable mid-infrared photodetectors based on asymmetrically doped coupled quantum well GaAs/AlGaAs structures. The peak of photoresponse detection varies from 7.5 to 11.1 µm when switching bias from -5 to +5 V. The spectral tunability is defined by the interplay of several effects. First, the electron energy levels are shifted due to the Stark effect. Second, the applied electric field causes the charge redistribution in the coupled wells and shift of electron energy levels due to modification of self-consistent potential. Here we show that effect of electric field on tunneling processes (the Poole–Frenkel effect) and the field-induced decrease of thermo-emission barrier (the Fowler–Nordheim effect) also play a critical role in photoelectron kinetics, strongly enhancing the carrier extraction from quantum wells. The model which takes into account Poole–Frenkel and Fowler–Nordheim effects provides a quantitative description of the data obtained.