Planar cold cathodes

There is a great need for electron sources for a variety of applications, such as klystrons, traveling wave tubes (TWTs), planar panel displays, vacuum triodes, etc.. The cold cathode electron emitters under investigation currently can be basically divided into two types: field emitters and planar emitters. Field emitters are based on the field emission mechanism which was first presented by Fowler and Nordheim in 1928. In planar emitters, electrons are accelerated inside solid state materials by internal electric field. Those electrons which reach the surface with enough kinetic energy to overcome the surface work function could be emitted into vacuum. A lot of work has been done in this area and many planar emitters based on different hot electron generation mechanisms have been described in the past 30 years. To obtain considerable emission efficiency and current density, the solid state surface is usually coated with low work function material (on the order of one mono-layer), such as cesium and cesium oxide. This paper reviews the developments of planar cold cathodes and discusses the characteristics of AlGaAs/GaAs planar doped-barrier electron emitters (PDBEEs) based on the study of their temperature dependent current-voltage (I-V) characteristics