Monolithically integrated active cooling is an attractive way for thermal management and temperature stabilization of microelectronic and optoelectronic devices. SiGeC can be lattice matched to Si and is a promising material for integrated coolers. SiGeC/Si superlattice structures were grown on Si substrates by molecular beam epitaxy. Thermal conductivity was measured by the 3 method. SiGeC/Si superlattice microcoolers with dimensions as small as 40ϫ40 m 2 were fabricated and characterized. Cooling by as much as 2.8 and 6.9 K was measured at 25°C and 100°C, respectively, corresponding to maximum spot cooling power densities on the order of 1000 W/cm 2 . © 2001 American Institute of Physics. ͓DOI: 10.1063/1.1356455͔Thermoelectric ͑TE͒ refrigeration in a solid-state active cooling method with high reliability. Bi 2 Te 3 -based TE coolers are widely used for cooling and temperature stabilization of microelectronic and optoelectronic devices, but their processing is a bulk technology and is incompatible with integrated circuit fabrication process. Solid-state coolers monolithically integrated with microelectronic and optoelectronic devices are an attractive way to achieve compact and efficient cooling. It can lower the cost of fabrication and packaging, and can selectively cool individual key devices instead of the whole chip. However, the thermoelectric figure of merit ͑ZT͒ is quite low for most of the semiconductors used in microelectronics and optoelectronics. This makes it difficult to get high cooling performance. Recently heterostructure thermionic and superlattice coolers have been proposed, and theoretical calculations show that large improvements in ZT can be achieved and efficient refrigeration becomes possible with coolers made of conventional semiconductor materials.