Thermoelectric Cooling of Photodetector Arrays with HgCdTe-based Superlattices

The most challenging degrading effect on current state-of-the-art focal plane arrays is caused by the random spatial and temporal photoresponse nonuniformity of the pixels. We propose a major improvement by controlling the temperature of individual pixels with individual thermoelectric coolers. We will use HgxCd1-xTe/HgyCd1-yTe superlattices (SLs) as the thermoelectric material. Two major benefits lead us to this choice. First, HgCdTe, the principal material used in infrared photon imaging applications, can be directly grown on HgxCd1-xTe/HgyCd1-yTe SLs, making the integration of infrared sensors and thermoelectric elements possible. Second, a recent model showed that a Hg0.75Cd0.25Te/Hg0.7Cd0.3Te SL can achieve a thermoelectric figure of merit ZT of 1.99, two times greater than that of current thermoelectric devices based on Bi2Te3. In Phase I, we will develop an accurate model of the thermoelectric properties of HgxCd1-xTe/HgyCd1-yTe SL structures and we will optimize the material parameters to maximize ZT. Next, we will address the growth of HgxCd1-xTe/HgyCd1-yTe SLs by partnering with the University of Illinois at Chicago, which has extensive experience with the growth of HgTe/CdTe SLs and HgCdTe. Finally, we will develop device structures and metallization methods for performing ZT measurements, measure ZTs of the devices and compare them to theory.