Multiple quantum well superlattice infrared detector with low dark

Abstract

A multiple quantum well (MQW) radiation sensor eliminates tunneling current from the photoactivated current that provides an indication of incident radiation, and yet preserves a substantial bias voltage across the superlattice, by fabricating an intermediate contact layer between the superlattice and a tunneling blocking layer. Using the intermediate contact layer to apply a bias voltage across the superlattice but not the blocking layer, the photoexcited current flow through the intermediate contact and blocking layers is taken as an indication of the incident radiation. The width of the intermediate contact layer and the barrier energy height of the blocking layer relative to that of the superlattice barrier layers are selected to enable a substantial photoexcited current flow across the blocking layer. The thickness of the intermediate contact layer is preferably not more than about 1 photoexcited charge carrier mean-free path length, while the blocking layer's barrier energy height is preferably at least about 1 phonon energy level below that of the superlattice barrier layers.