GaAs/AlGaAs quantum-well photodetector for visible and middle infrared dual-band detection

We present experimental results on quantum-well photodetectors for visible and infrared dual-band detection. Large band gap top contacts were used on a standard GaAs/AlGaAs quantum-well infrared photodetector so that visible light could reach the quantum-well region and be absorbed via interband tra nsitions. Two designs were investigated, using a high Al fraction AlGaAs an d a short period GaAs/AlAs superlattice contact layer. The dual-band respon se spectral regions are 0.55-0.7 and 7-10 mu m. Measured responsivities are about 0.7 A/W at 8.3 mu m and 0.1 A/W at 0.63 mu m under -6 V bias voltage . (C) 2000 American Institute of Physics. [S0003-6951(00)00642-2].