High-power on-chip microrefrigerator based on a normal-metal/insulator/superconductor tunnel junction

We present measurements and theoretical modeling of two normal/insulator/superconductor tunnel junction microrefrigerators. The first device, fabricated on a thick silicon substrate, had a cooling power of 36 pW, an active volume of 350 mu m(3), and a temperature drop for electrons of 2 mK from a 300 mK bath. The second device, fabricated on a thin silicon nitride membrane, had a cooling power of 4 pW and cooled both electrons and phonons in a similar volume by almost 2 mK from a bath of 300 mK. These are the largest cooling powers and active volumes for electron and phonon refrigeration reported to date. (C) 1999 American Institute of Physics. [S0003-6951(99)04818-4].