Two-color infrared detection using intersubband transitions in multiple step quantum wells with superlattice barriers

A dual-band multiple quantum well infrared photodetector has been fabricated for the near and mid-infrared detection. The structure consists of InGaAs/GaAs step quantum wells separated by AlGaAs/GaAs superlattice barriers. The step quantum wells are designed to have two bound states and a quasi-continuum above the superlattice barriers. The bound-to-bound and bound-to-continuum transitions are employed for the dual-band detection. The superlattice barriers are used to extract the photocurrent from the bound-to-bound transition with a relatively low external electric field, which keeps the dark current low. This work demonstrates the use of a new quantum well structure for the fabrication of multicolor quantum well infrared photodetectors.