Photovoltaic and photoconductive infrared detectors

Photovoltaic and photoconductive infrared detectors offer very high detectivities, although they must often be cooled. The continuing improvement of detector performance is related to the development of highly purified, single-crystal semiconductors as their active materials. Aspects of basic theory are examined, taking into account direct photon detection, photocurrent, gain, responsivity, noise mechanisms, detectivity, response time, and problems of electrical power dissipation. The important photovoltaic detectors use intrinsic photoexcitation. General relations regarding their theory are discussed. Attention is given to suitable photovoltaic infrared detector material, the theory and the materials used in the case of intrinsic photoconductive detectors, and the characteristics of extrinsic photoconductive detectors.