Characteristics of indium doped silicon infrared detectors

Interest in extrinsic doped silicon infrared detectors for operation in the mid-infrared (i. e., 3- to 5-μm spectral band) has recently been growing because of the benefits provided by employing silicon technology. The photo-ionization cross section of Si:In operated at temperatures greater than 77°K has been previously measured. This paper presents data on the signal-to-noise ratios (SNR) at temperatures from 4° to 70°K under two conditions of background photon flux density and detector bias. This data was taken from a specimen with an indium doping of 2.7 × 10¹⁷ cm^-3, Quantum efficiencies of 50 percent were measured. Detectivity, D*, as a function of temperature decreased by about 10 percent at 55°K and was even less at 70°K. Mobility data in conjunction with the measured responsivity data is used to determine the hole lifetime. It has been found that this lifetime increases as the temperature increases. Lucovsky⁽¹⁾ has presented a model of the spectral response expected because of deep impurity levels. The measured spectral response data is in quite good agreement with that predicted by theory.