Exponential-doping III–V photocathodes with negative electron affinity

With the limitation of epitaxial growth technique, the approximately exponential-doping structure is actually a special kind of gradient-doped structure, in which the doping concentration in the active-layer of the III-V photocathode varies exponentially from bulk to surface. This doping structure can result in a linearly downward band structure which helps form a constant built-in electric fields to facilitate photoexcited electron movement towards surface, and the band structure of the exponential-doping photocathode is shown in this paper. By using the MBE technique, the reflection-mode (RJVI) and transmission-mode (TM) exponential-doping GaAs photocathodes composed of many sublayers were grown.