Structured cold point thermoelectric coolers

Abstract

Solid-state thermoelectric coolers can revolutionize thermal management of electronics and optoelectronic systems, and small-scale refrigeration if the coolers could attain thermodynamic efficiency greater than 30% of the ideal Carnot cycle. The maximum temperature differential and the efficiency of thermoelectric coolers are known to depend on material properties through the thermoelectric figure-of-merit ZT=S2σT/λ. Z has units of inverse temperature, and depends on the Seebeck coefficient S, the electrical conductivity σ, the thermal conductivity λ, and the temperature T. The efficiency requirements imply that the figure-of-merit needs to be increased from ZT∼1 typical of bismuth chalcogenides at room temperatures to ZT>3. The cooling power per unit area is only dependent on the critical transport length of the thermoelement and can easily exceed 50 W/cm2 in thin-film cooler structures (U. Ghoshal and R. Schmidt, ISSCC Dig. Tech. Papers, vol. 43, p. 216, 2000). We have been investigating the scaling properties of thin-film thermoelectric coolers, and the properties of structured point contacts at the cold end (Y.S. Ju and U. Ghoshal, J. Appl. Phys., vol. 88, p. 4135, 2000).