ULTRA-HIGH PERFOMANCE SOLID-STATE REFRIGERATION USING II-VI LOW DIMENSIONAL STRUCTURE

ABSTRACT: This program targets development of a high-performance thermoelectric (TE) cooler with a figure-of-merit, ZT>3, which greatly exceeds currently available technology. The cooler is fabricated using Group II-VI compound semiconductors, i.e. HgCdSe or HgCdTe, using a low dimensional structure know as a"superlattice"(SL). The proposed TE coolers will operate at temperatures ranging from 50K to 300K, thereby providing a fundamentally new and disruptive method for achieving cryogenic cooling. In fact, currently no solid-state refrigerator can provide sufficient cooling for high-performance infrared (IR) detectors or that can cool from room temperature down to the transition temperature of superconductors or similar systems. In addition, applications involving the thermal management of high performance II-VI based infrared (IR) sensors and focal-plane arrays (FPAs) are well suited to this technology since the cooler is fabricated using similar materials. This enables monolithic integration of the FPA and cooler leading to extended component lifetime and a very fast cooling response. Furthermore, standard integrated-circuit batch fabrication techniques can be used to economically manufacture the integrated coolers. Amethyst works closely with Teledyne, Raytheon, and FLIR to ensure that this technology can be rapidly integrated into DoD platforms. BENEFIT: The application of infrared sensors and FPAs in civilian, military, and scientific endeavors is growing rapidly. Large staring HgCdTe MWIR/LWIR cameras have excellent image quality and high sensitivity, and are a natural choice for surveillance and targeting at medium and long ranges. With the proliferation of large numbers of unmanned mobile assets to the battlefield, there are strategic intelligence functions (such as IR reconnaissance, surveillance, targeting, and red/blue-force tracking) that cannot be integrated because the platforms cannot support the size, weight, limited-lifetime and cost of the present Stirling cooler technology. Also, similar issues relating to size, weight and cost limit market expansion in commercial applications such as medical diagnosis, environmental and chemical process monitoring, and astronomical imaging. Thus, availability of a light-weight, economical thermoelectric cooler with ZT>3 at T down to 50 K will provide an immediate benefit to a wide range of high-performance IR imaging systems. One such system is the Army"s Micro-Autonomous Systems and Technologies, which is developing agile unmanned platforms to perform high-risk Army imaging functions. Another system is the Army"s Passive IR Cueing Sensor program - a threat-warning system based on classifying the IR launch signature of hostile inbound threats to ground and air platforms. The lower cost of SL coolers would lead to widespread deployment of these systems.