Phenomenological treatment of the nonlinear optical response at metal-semiconductor interfaces

A phenomenological theory is presented that describes the nonlinear optical response at metal-semiconductor interfaces. The metal-semiconductor interface is represented by a jellium-dielectric contact. We employ a generalized Thomas-Fermi model to describe the jellium and explicitly take into account Schottky-barrier formation at the interface. The nonlinear response is shown to depend essentially on three parameters: the metal work function, the semiconductor electron affinity, and the Schottky-barrier height at the interface. We discuss the dependence on the bias potential and overlayer thickness of the optical second-harmonic response of metal overlayers on semiconductor substrates.