Thin film infrared detector arrays for integrated electronic structures

Abstract

A new technique to obtain high quality middle i.r. detector arrays has been developed by the use of r.f. sputtering. Ternary chalcogenide layers with interesting properties for fabricating multielement detector arrays have been deposited by r.f. sputtering. Single crystal and polycrystalline Pb xSn 1−xTe and PbTe films have been investigated in the course of developing bidimensional detector arrays. Polycrystalline photoconductive detectors with exceptional responsivity and detectivity values have been obtained by means of reactive sputtering of PbTc and Pb xSn 1−xTe layers in an oxygen-tellurium-argon plasma atmosphere. This technique has allowed us to control the impedance and time constant values of the detectors in a very wide range just controlling the oxygen content in the gaseous sputtering plasma. Oxygen sensitizing effects in the photoconductive process are evidenced by Hall mobility, lifetime and spectral response vs temperature from room temperature down to liquid nitrogen. Photovoltaic properties of Pb xSn 1−xTe Ge heterojunctions are reported and discussed. These results are particularly important because silicon and germanium substrates can be used for incorporating the electronic readout elements, for both electronic switching and signal amplification, utilizing integrated cryogenic amplifiers and scanning circuits. Moreover high level performances can be achieved by integrating the high impedance policrystalline detectors into charge-coupled-device imaging systems.