Simulation of room temperature thermionic emission from AlxGa1−xN negative electron affinity cathodes

A cathode consisting of AlxGa1−xN is theoretically investigated. Spatial variations of Al fraction are used to provide a structure which transports electrons from n-type GaN material to Al0.75Ga0.25N material which exhibits negative electron affinity. The simulations indicate the emitted electron current density corresponding to various applied fields. The results for structures in which a 75-nm-thick layer of compositionally graded AlxGa1−xN sits upon a 100-nm-thick layer of GaN indicate that at room temperature a thermionic emission current density on the order of 100 A/cm2 can be expected for an applied field of about 75 V/μm. These new results indicate that AlxGa1−xN compositionally graded cathodes should be useful for vacuum microelectronic devices.

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