Theory of Internal Photoemission

Fowler's hypothesis commonly used to interpret results of photoemission into the vacuum has been extended to deal with the problem of internal photoemission. This leads to the empirical relation $Y\propto {(E-E_t)}^2$ between the quantum efficiency $Y$ and the photon energy $E$, currently used to interpret hole photoemission experiments. $E_t$ is the threshold energy for photoemission. Various cases of internal electron and hole photoemission between metals and semiconductors are discussed.