Structured cold point thermoelectric coolers

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=S/sup 2//spl sigma/T//spl lambda/. Z has units of inverse temperature, and depends on the Seebeck coefficient S, the electrical conductivity /spl sigma/, the thermal conductivity /spl lambda/, and the temperature T. The efficiency requirements imply that the figure-of-merit needs to be increased from ZT/spl sim/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/cm/sup 2/ 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).