Patent ID: 6838669

Claim:
A system for detecting presence of thermal radiation, the system comprising: a module of silicon (Si), having a region doped with In, having a dopant fraction f(In) in the semiconductor material in a range, 5×10 −11 ≦f(In)≦5×10 −6 ; a coating for the doped region that absorbs substantially all radiation having a wavelength below a photoconductivity cut-off wavelength for Si doped with In and is at least partly transparent to radiation having at least one wavelength above the photoconductivity cutoff wavelength so that substantially no radiation having a wavelength below the photoconductivity cutoff wavelength is received by the doped region; and a circuit connected to the doped region at first and second spaced apart locations, to receive at least one electrical signal that passes within the doped region, and to provide a measure of at least one of (i) current passing through the doped region and (ii) a voltage difference measured between two selected locations within the doped region; whereby the circuit provides a first value of the at least one of the current and the voltage difference when radiation, from a selected source having at least one wavelength in the infrared spectrum is received by the doped region and provides a second value of the at least one of the current and the voltage difference if the radiation is not received by the doped region, over a module temperature range from 20 K to 300 K.