HIGH-EFFICIENCY PHOTOEMITTERS OF GaAs PREPARED BY LIQUID-PHASE EPITAXY IN HIGH VACUUM.
The work function at the surface of some P-type semiconductors can be reduced so that it does not exceed the value of the energy gap of the bulk (Negative Electron Affinity, NEA). Efficient electron emitters produced in this way have found application as photocathodes, secondary electron emitters and cold cathodes. A brief summary of present NEA theories is given and the techniques employed to realize NEA are described. Experimental results in growing high-efficiency photocathodes made of Ge-doped P-GaAs films using a special liquid phase epitaxial process in a high-vacuum furnace are presented.