Theory of internal photoemission in sandwich structures

The internal photoemission in sandwich structures is treated as a multi-step process. The excitation functions for electrons in the electrodes are obtained as a result of a rigorous optical analysis of the light propagation and absorption. The electron-electron and electron-phonon interactions are described in terms of energy-dependent mean free paths. The calculation of the quantum. yield and photocurrent includes the electrons which escape without scattering, after one scattering, and after two scattering processes. In calculating the probability for electrons to escape over the inner potential barrier within the structure account has been taken of both their being scattered within the barrier region and their quantum-mechanical character. The present calculations can convenietly be used for theoretical investigations of the photoemission in its dependence on various parameters of the structure. The formulae also retain their validity for the photoemission of holes when the quantities due to electrons are correspondingly replaced. An adaptation of the theory to the vacuum photoemission from thick as well as very thin samples is possible without difficulties.