Electron-optical-phonon scattering in the emitter and collector barriers of semiconductor-metal-semiconductor structures

A theoretical analysis is made of the effects on the emitter-collector current transfer ratio of optical-phonon scattering of electrons in the emitter and collector semiconductors of semiconductor-metal-semiconductor structures. The collector and emitter efficiencies are shown to increase appreciably with increasing collector and emitter electric fields respectively. At temperatures such that kT ≈ the optical-phonon energy, E₀, the collector efficiency varies only slightly with increasing emitter-collector barrier height difference, Δ, but the emitter efficiency is greatly decreased when Δ<E₀. The collector and emitter efficiencies increase substantially with decreasing temperature when Δ<E₀, but only slightly when Δ>E₀.

The current transfer ratios predicted by this theory for Si---Au---Si and GaAs---Au---Si structures are 0·68 and 0·55 respectively at 298°K and 0·85 and 0·61 respectively at 105°K with a collector field of 10⁵ V/cm. This calculation does not treat collisions in the metal or quantum-mechanical reflection of electrons at the collector barrier.