Monolithic silicon mosaics for far-infrared imaging

Monolithic detector mosaics were constructed for image sensing at wavelengths from three to 30 µm. The mosaics use impurity photoconduction in silicon to sense infrared radiation. Operation in the 25 to 40°K temperature range is obtained with closed-cycle cooling. Photosensor elements, spaced on 32 mil centers, are formed by solid-state diffusion, and a junction diode is constructed in series with each photoresistor to reduce crosstalk. The integrated 30-by-30 mosaics have crossed
X-Y
electrodes for direct-wire readout of picture elements. Performance of individual elements is described. At 25°K, a detectivity of 1 × 10
⁸
cm Hz
^1/2
/W per element is found using 10.6 µm CO
2
laser radiation. The quantum efficiency at 10.6 µm is about 7 percent, and the response time is observed to be less than 0.2 µs. Uniformity and crosstalk data on prototype arrays are presented, and the integration of these arrays with cryogenic amplifier and scanning circuits is discussed.