Non-Cesiated Solid State Electron Emitters (Cold Cathodes) & Their Applications in Vacuum Microelectronics

Abstract : Stable, non-cesiated cold cathodes hold much promise for high power and high efficiency vacuum electronics. Cesium is typically used to lower the surface barrier to electron emission, but cesium presents problems with reliability and lifetime. GaN-based cold cathodes have the advantage of having a low surface barrier and a stable surface, both of which are beneficial for cold cathode electron emission. Better performance, in terms of lower operating voltage and higher current density, can be achieved by further decreasing the size of the surface tunnel barrier of field emitter-based cold cathodes. The large piezoelectric field produced in pseudomorphically grown InGaN layers on GaN field emitter pyramids allows the reduction of the surface energy barrier. Experiments have shown that the amount of barrier lowering increases with increasing InGaN thickness up to some critical thickness where the effects of strain relaxation and scattering reduce the effect of the piezoelectric barrier lowering. Results of an experiment have shown an effective electron affinity of 1 eV, which is reduced 70% from the electron affinity of GaN, 3.5 eV. The effective of the electron affinity reduction is to reduce the turn-on voltage of the field emitter arrays, from 300 V to 150 V.