480 × 8 hybrid HgCdTe infrared focal plane arrays for high-definition television format

Abstract

We explain the technologies used for high-performance long linear arrays based on HgCdTe/CMOS hybrid multiplexers with bidirectional time delay and integration (TDI) functions and describe the development of the first high-resolution IR imaging system with a superextended graphics array (SXGA) format. Long-wavelength IR photodiode arrays are fabricated using liquid-phase epitaxially grown HgCdTe on a CdZnTe substrate. Each photodiode array consists of 480x8 element n+/n-on-p diodes formed by B+ implantation. Diodes with a 10.3-μm cutoff wavelength have a typical zero-bias resistance of 10 MΩ and a shunt resistance of 1 GΩ. Four CMOS readout integrated circuits (ROICs) are used for bidirectional TDI and multiplex operations, where each ROIC sums up and multiplexes eight signals from 120 channels. The ROIC also includes pixel deselection and gain control circuits along with the corresponding memory and writing means. The IR focal plane arrays (IRFPAs) have a typical noise equivalent temperature difference (NETD) of 18 mK after TDI with F/1.55 optics and 10-μs integration. The IR imaging system adopts an interlace scan using the 480x8 element IRFPA to demonstrate a high spatial resolution of 1280 horizontal lines by 960 vertical lines (SXGA format) and an NETD of less than 30 mK. The unique algorithm for image enhancement is successfully confirmed to be efficient.