Wide Operational Range Thermal Sensor

Bolometer system and method for detecting, at BLIP levels, presence of radiation over a broad range of wavelengths in an infrared spectrum and in a temperature range from 20 K to as high as room temperature. The radiation is received by a Si crystal having a region that is doped with one or more of In, Ga, S, Se, Te, B, Al, P, As and Sb in a concentration ratio in a range such as 5 x 10(exp -11) to 5 x 10(exp -6). Change in electrical resistance delta R due to receipt of the radiation is measured through a change in voltage difference or current within the crystal, and the quantity delta R is converted to an estimate of the amount of radiation received. Optionally, incident radiation having an energy high enough to promote photoconductivity is removed before detection.