SiGe/Si superlattice coolers

The fabrication and characterization of SiGe/Si superlattice coolers are de scribed. Superlattice structures were used to enhance the device performanc e by reducing the thermal conductivity between the hot and the cold junctio ns, and by providing selective removal of hot carriers through thermionic e mission. Cooling of 2.2 K and 2.5 K were measured on n-type and p-type 75 x 75 mu m(2) devices, corresponding to cooling power densities of hundreds o f watts per square centimeter. Cooling up to 7.2 K was obtained at 150 degr ees C for p-type 50 x 50 mu m(2) devices. The results show that n-type and p-type coolers can work together in similar optimal conditions. This paves the road to fabricate n-type and p-type superlattice coolers in an array fo rmat electrically in series and thermally in parallel, similar to conventio nal thermoelectric devices, and thus achieve large cooling capacities with relatively small currents.