Refrigeration With And Of Solid State Devices

Abstract

Solid state coolers are reliable, cheap and easy to scale down to microscopic scales, hence very promising for on chip refrigeration in microelectronics. The previous decade has shown tremendous interest for applications both in science and industry. In this thesis we present an overview on the state of the art possibilities and applications of solid state cooling in Microelectronic industry. A study based on the different types of coolers, their applicability and limitations. This includes the operating temperature ranges, cooling power and effciency. Physical and practical advantages and drawbacks of different systems are analysed. Also presented is a brief literature on cryogenic NIS coolers, their operating principles,effiencies, and limitations are touched upon. In that respect, the problems limiting the effiency of these refrigerators is the excessive heating, of the superconducting leads. The diffusion of hot quasi-particles is of critical importance. The physical processes behind are of strong fundamental interest, especially at low temperatures. To address the above problem of heating, we conduct an experiment which allows us to study the diffusion and energy relaxation of quasiparticles in a superconducting wire which aids in the design and optimization of the NIS coolers. An attempt has been made identify the relevant physical processes involved. This involves study of nonequilibrium superconductivity, tunnelling, diffsion and relaxation processes. We present the the basic physics, fabrication technology and experimental techniques.