Comparative research on electron diffusion length for GaAs photocathodes

The feasibility of measuring the electron diffusion length of photocathodes by surface photovoltage spectroscopy from theory and deduce the calculation formulas. The principle of the surface photovoltage spectroscopy method and the measuring technique are discussed particularly using the electro-static equilibrium condition and the law of conservation of charge on the basis of the energy band structure of semiconductor. The measurement of spectrum respond wave after activiation and surface photovoltage spectroscopy are shown. The difference between the two curves and the diffusion length fitted by the two curves are discussed. Thus the development of closed-loop research for GaAs photocathodes through surface photovoltage spectroscopy before activation and spectrum respond wave after activation are developed.