Low Temperature Thermoelectric Cooling of Infrared Focal Plane Arrays with HgCdTe-based Superlattices

The deployment of next generation focal plane arrays sensing in the long wavelength infrared will improve the detection capabilities in all major MDA infrared systems. However, a major limitation to the employment of these high sensitivity arrays is the cooling system. Current tactical cryocoolers cannot meet the desired temperature requirements. The goal of this project is to develop the technology required for the fabrication of thermoelectric devices capable of cooling the infrared arrays from 65 K to 35 K and to integrate them with current-generation cryocoolers that reach 65 K. We propose the development of nanoscale superlattices (SLs) as the active elements of high efficiency thermoelectric coolers. Recent models predict that the HgCdTe-based SL room temperature thermoelectric figure of merit ZT can exceed 6. The feasibility of using HgCdTe-based SL materials with embedded nanodefects for increased hot-carrier transport will be demonstrated in the proposed Phase I program. We will perform calculations to optimize material parameters to maximize ZT. We will use our extensive experience in molecular beam epitaxy to grow the designed structures. Finally, we will develop device structures and metallization methods appropriate for performing ZT measurements, measure the ZTs of fabricated devices and compare results with theory.