Patent ID: 7800067

Claim:
A photovoltaic detector comprising: a semiconductor graded absorber layer adapted to generate charge carriers through interaction with infrared (IR) radiation, the graded absorber layer having a composition grade; a semiconductor collector layer adapted to collect the charge carriers; a semiconductor selector layer adapted to selectively deplete the graded absorber layer, the selector layer having a same doping type as the collector layer and an opposite doping type as the graded absorber layer, wherein the composition grade of the graded absorber layer is away from the selector layer such that a narrower band gap absorber material is closer to the collector layer and a wider band gap absorber material is closer to the selector layer, wherein the electromagnetic radiation to be detected enters the graded absorber layer through the selector layer, wherein the magnitude of the reverse bias applied to a p/n junction composed of the selector layer and the absorber changes the spectral response of the detector, wherein the graded absorber layer is interposed between the collector layer and the selector layer, wherein the graded absorber layer contacts the collector layer and the selector layer, wherein independent electrical contacts are respectively made to the selector layer, the graded absorber layer, and the collector layer to permit the biasing of two p/n junctions independently, wherein the electrical contacts made to the selector layer and the graded absorber layer selectively remove photogenerated carriers created within a depletion region of the graded absorber layer and noise currents created within the depletion region of the graded absorber layer; and a bias voltage source electrically coupled to the selector layer and the graded absorber layer and adapted to tune a depletion width of the graded absorber layer.