The silicon cold cathode

Cold cathode emission has been obtained from forward-biased silicon p-n junctions whose p-surfaces were activated to a state of negative electron affinity. In operation, electrons injected into the p-layer diffuse to the surface where they are emitted into vacuum. An Si:SiO2structure has been developed to overcome the problems associated with current crowding, and with this structure, efficiencies (ratio of emitted current to bias current) as high as 10 percent have been observed. Emitted current densities as large as 225 A/cm²and currents as large as 7 mA have been drawn under pulsed conditions, while continuous current densities of 2 A/cm²and currents of tens of microamperes have been drawn for many hours. The electrical characteristics exhibited space-charge-limited and emission-limited regimes as well as Schottky effect. The silicon cold cathode has advantages in applications such as vidicons, where some aspects of performance are presently limited by the thermionic cathode, and where power consumption and heat generation must be minimized.