/Hg,Cd/Te photodiodes for detection of two-micrometer infrared radiation

Infrared detectors using mercury-cadmium telluride photodiodes capable of operating at moderate temperatures are described. Features of the diodes include: ability to detect infrared in the 1.5 and 2.0 micrometer region; low noise current over a range of frequency; and a current response which is linear with incident power. Low capacitance of the mercury-cadmium telluride photodiodes permits high frequency operation; while in operations involving large numbers of the diodes, the array displays excellent uniformity of detection and responsivity. Tests indicate that detectors using photodiodes with cutoffs in the 2.0 to 2.3 micrometer spectral range have achieved increasingly high detectivities as temperature is decreased from 300 K to 193 K. This high detectivity rate at moderate temperatures is important for satellite applications, since cooling of detectors requires large and heavy radiative coolers.