Photovoltaic intersubband photodetectors using GaAs quantum wells confined by AlAs tunnel barriers.

We have found experimental evidence that the tunneling processes which are crucial to the detection properties of these devices are not only controlled by the thickness of the AlAs tunnel barriers but are significantly influenced by an additional asymmetry involving the scattering behavior of the carriers. This contribution presumably arises from a difference in the interface roughness on both sides of the GaAs quantum well. Our experimental findings indicate that detector structures with the electron transport occurring towards the substrate side give rise to better photovoltaic behavior than devices with the other transport direction. Studies concentrating on the physics behind these scattering processes are promising for further improvement of photovoltaic detector operation.