Low-temperature thermionic emitters using metal-semiconductor composites

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Small metal particles (10–100 nm in size) buried in semiconductor matrices provide a source of electrons which can be optically or thermally excited into the semiconductor across the metal-semiconductor Schottky barrier. These electrons which are now in the conduction band of the semiconductor have only to surmount the surface barrier of the semiconductor, i.e. the electron affinity EA, in order to escape into vacuum. Since Schottky barriers can be made considerably smaller than the bandgap Eg of most common semiconductors (1–3 eV), the threshold for electron emission into the vacuum is reduced, i.e. (ESchottky+EA)<(Eg+EA). Some preliminary results on Au-CuInSe2 composites provide strong support for these ideas.