Development of a 100 Milli-Kelvin electronic refrigerator based on a normal-insulator-superconductor tunnel junction

We report recent progress on an all-electronic, on-chip, 100 mK refrigerato r. This refrigerator utilizes the unique thermal transport properties of a normal-insulator-superconductor (NIS) tunnel junction to preferentially rem ove electrons whose energy is higher than the Fermi energy from the normal electrode, and thus, to lower the temperature of electrons in the normal el ectrode. We present the first measurements demonstrating electron cooling i n a device having a substantially larger area (similar to 10(4) pm?) than t ypical submicron-scale devices demonstrated previously. The performance of this refrigerator is analyzed by a simple thermal model that includes energ y transport through the junction, thermal loading from the environment, rec ombination of quasiparticles in the superconductor electrode, and non-ideal junction characteristics. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.