A novel electron emitter with AlGaAs planar doped barrier

Hot electron emission from a planar surface has been pursued in the past two decades in both silicon and III-V compound semiconductors. Since they are majority carrier devices and have controllable material growth by MBE, emitters made from planar doped barrier (PDB) structures have the advantages of high current density and high electron emission efficiency. The authors present the emission from a new Al/sub 0.3/Ga/sub 0.7/As-GaAs PDB emitter. A PDB structure consists of a sequence of n/sup +/-i-p/sup +/(delta-doped)-i-n/sup +/ layers. The p/sup +/ delta-doped sheet is fully depleted giving rise to a triangular barrier. A positive bias applied to the surface forward biases the n/sup +/-i-p/sup +/ injecting junction and reverse biases the p/sup +/-i-n/sup +/ accelerating junction so that electrons in the n/sup +/ region are injected across the barrier into a high field region and accelerated toward the surface. Electrons with kinetic energy larger than the surface work function are then emitted. For an efficient PDB emitter, the transit distance (the total thickness of the accelerating region and the top contact layer) should be small and the accelerating voltage (the voltage drop across the accelerating region) should be large. The breakdown of the accelerating junction sets an upper limit to the field applied to the accelerating region. One way to increase the accelerating voltage and hence the electron kinetic energy, without sacrificing the small transit distance, is using materials with a higher breakdown field.<>