Mid-wavelength infrared detection with InxGa1-xAs/Al0.45Ga0.55As multiple quantum well structures

We demonstrate the detection of mid-wavelength (3-5 mu m) infrared radiation by intersubband transitions in In x Ga 1-x As/Al 0.45 Ga 0.55 As multiple quantum well structures grown on GaAs substrates. The peak detector response is shifted from 4.8 to 4.3 mu m by increasing the indium fraction from x=0.05 to x=0.20, while simultaneously decreasing the well width to keep the first excited eigenstate near the top of the wells. These detectors can be combined in detector stacks with conventional long-wavelength (8-12 mu m) infrared quantum well detectors for multi-band imaging applications.