Polycrystalline PbSe x-y addressed uncooled FPAs

Abstract

A technology for processing low density uncooled focal plane arrays (FPAs) of polycrystalline PbSe has been developed. PbSe is deposited, processed and sensitized on a silicon substrate with two levels of metal separated by a thin dielectric layer of SiO₂. An x-y addressed type read out permits a reduced number of leads and high filling factors. Unlike standard polycrystalline PbSe processing method we deposit PbSe by sublimation in vacuum. As-deposited, PbSe is not sensitive to IR light. In order to turn it photosensitive it is necessary to expose the films to specific thermal treatments. We have developed a very efficient sensitization process during which substrates withstand temperatures as high as 450°C. As a technology demonstrator, a low density (8x8 elements) PbSe FPA has been processed. Room temperature detectivities typically yield values of Dλ* (500 K, 300 Hz, 1.2 Hz) approximately 3 x 10⁹ cm Hz^1/2/W. The technological capabilities developed can be easily extended to more dense arrays.