Calculation of heterojunction conduction band for a field-assisted InP/InGaAsP/InP semiconductor photocathodes

By using the hyperbolic grading function and taking account of the potential variation near the surface of photocathode caused by an applied bias, the conduction band structure at the heterojunction interface for a field-assisted InP/InGaAsP/InP semiconductor photocathode were analyzed and calculated. The profile curves of conduction band structure at the heterojunction interface with different parameters of materials were obtained. In order to achieve the perfect transmission efficiency at heterojunction, the calculation results have shown the conditions for the thickness and the doping concentration of the emission layer, the doping concentration of the absorption layer, as well as the grating width at the heterojunction interface and the applied bias. The results are helpful to designing a field-assisted semiconductor photocathode.