Dual-band photodetectors based on interband and intersubband transitions

We present experimental results on quantum-well photodetectors for visible or near-infrared and middle- or far-infrared dual-band detection. We report on two types of devices based on (1) InGaAs/InP and (2) GaAs/AlGaAs quantum wells. In the first case, InGaAs/InP quantum-well infrared photodetectors (QWIPs) for both near and middle infrared spectra are shown. In the second case, large bandgap top contacts were used on standard GaAs/AlGaAs QWIPs so that visible light could reach the quantum-well region and be absorbed via interband transitions. Two large band gap top contacts were investigated, using a high Al fraction AlGaAs and a short period GaAs/AlAs superlattice. We evaluate and analyze the detector performance. We find that such devices are potentially useful for applications involving dual-band simultaneous detection and imaging.