Thermionic Refrigeration

Abstract

The flow of current that gives rise to thermoelectric effects is diffusive. However, it is possible to obtain similar effects when ballistic flow takes place. This distinction is easily recognized when we compare the current in a vacuum diode with that in a bulk semiconductor. Ballistic type of flow is then called thermionic transport. This type of transfer can also take place in the solid state, and it is possible for diffusive effects in a semiconductor to give way to thermionic effects when the effective length between two barriers becomes very small [9.1]. Although there does not yet seem to be a practical refrigerator based on thermionic effects, there are good reasons for thinking that such a device will appear in the not too distant future. Thus, in this chapter, we discuss the basic physics of thermionic refrigeration. We treat transport both in a vacuum and in the solid state.