Transport asymmetry and photovoltaic response in -AlGa-As/AlAs/GaAs/-AlGa-As single-barrier quantum-wel infrared detectors.

We have studied the wavelength and electric-field characteristics of intersubband photodetectors where a thin AlAs tunnel barrier was introduced between one side of the GaAs quantum well and thicker layers of (AlGa)As. The photoresponse of these structures has an extremely broad (3-11 Mym) spectral range and there is a preferential escape direction of the photoexcited carriers towards one direction of the quantum wells giving rise to photovoltaic detector behavior. We found evidence that this transport asymmetry is not only caused by the asymmetric potential distribution, but that interface scattering processes are involved. These scattering processes act differently on the photocurrent and the dark current, which is useful for further optimization of quantum-well infrared detectors.