Optical Phonons in Metal-Semiconductor Tunnel Junctions

Abstract

A calculation of the conductance of a metal-semiconductor tunnel junction for which interactions with optical phonons occur in the semiconductor electrode is given. The calculation is based upon a Green's-function theory of Appelbaum, Brinkman, and Zawadowski. The conductance is found for a uniform self-energy and a spatially dependent self-energy. Although there is qualitative agreement between the present results and the main features of the transfer Hamiltonian formalism given by Davis and Duke, further analysis of the data on $p-\mathrm{S}\mathrm{i}$ indicates that barrier effects occur in addition to the electrode effects. On the basis of the doping dependence of the reverse-bias line shape in $p-\mathrm{S}\mathrm{i}$, it is suggested that a region of strong interaction with the optical phonons occurs in the barrier near the metal electrode at low doping levels.