Single quantum well intersubband infrared detector using GaAs-AlGaAs asymmetrical double-barrier structures

The authors investigate the possibility of long-wavelength infrared (LWIR) photodetection using a single quantum well in an asymmetrical double-barrier resonant tunnelling structure. The goal is to produce very fast (>10 GHz) LWIR detectors. GaA-AlGaAs structures with both Si-doped and undoped quantum wells designed for the 8-12 mu m wavelength region have been studied. Electrons responsible for the absorption are dynamically stored in the well for the undoped case under a finite bias voltage. A circuit-limited temporal response risetime of about 800 ps was observed. The device physics can be understood using a simple resonant tunnelling model. To compare with the experiments quantitatively, self-consistent numerical calculations have been carried out.