Multilayer Thermionic Refrigerator and Generator
  A new method of refrigeration is proposed. Cooling is obtained by thermionic emission of electrons over periodic barriers in a multilayer geometry. These could be either Schottky barriers between metals and semiconductors or else barriers in a semiconductor superlattice. The same device is an efficient power generator. A complete theory is provided. 
G.D. Mahan, J.O. Sofo, and M. Bartkowiak