Dark current reduction in a long wavelength quantum well infrared photodetector operating at low temperature

Defence and astronomy are particularly demanding applications of infrared focal plane arrays in the 8-20 μm range of wavelength. QWIP is a good candidate for the low flux applications. Dark current is clearly a limiting parameter for it. Therefore, we have studied the dark current at very low operating temperature where the electronic transport is in the tunneling regime. We have developed a model of transport based on hopping between localized states. In the tunneling regime of transport, we have identified the main role played by the interaction between electron and ionized impurities. Thus the dark current in the structure is sensitive to the doping profile (magnitude and shape). This paper is suggesting a new way of reduction of the dark current while keeping a constant absorption. A decrease of 50% of the dark current has already been achieved for specially designed components. An extra structure is presented and is leading to an even lower dark current.