Method of infrared radiation detection by uncooled photodetector

The article describes an optical method for detecting radiation in the far infrared region of the spectrum against the thermal noise background with an uncooled photodetector (PD) that is relevant for the field of indicator sensors. The basis of the PD is an abrupt anisotype heterojunction, made according to the “optical window–absorber” connection. The article considers the mechanism of the appearance of photocurrent components in a heterojunction during the absorption of long-wave radiation and their ratio. A measurement of the photocurrent in PD by incorporating a heterojunction into a bridge circuit is proposed. An analytical description of the dependence of the loop currents on the elements of the equivalent heterojunction circuit and the bridge measurement circuit is given. It is established that the functional dependences of the photocurrent components through the structural elements of the heterojunction are opposite in sign and intersect at the point of equality of their values. The method makes it possible to divide the currents in the heterojunction layers, calculate or set the current reference value by adjusting the measuring circuit and to provide the measurement of the photocurrent that is less than the thermal background in magnitude. An example of the practical implementation of the method in a heterojunction PD with the structure n(CdSe)–p(Pb1–xSnxSe) is presented