New Mechanism for Electron Emission from Planar Cold Cathodes: The Solid-State Field-Controlled Electron Emitter

A new mechanism for electron emission from planar cathodes is described. The theoretical analysis shows that, with an ultrathin wide band-gap semiconductor layer (UTSC) on a metal, the surface barrier is lowered to $\sim 0.1\mathrm{eV}$ due to the creation of a space charge induced by the electrons injected from the metal. The barrier height depends mostly on the UTSC thickness and not on the state of the surface, as in thermionic and field emissions. This mechanism explains the measured stable emission at 300 K and ${10}^{-7\mathrm{}}\mathrm{Torr}$, with a threshold field of only $\sim 50\mathrm{V}/\mu \mathrm{m}$, from these solid-state field-controlled emitters.