QUANTUM EFFICIENCY OF SCHOTTKY PHOTODIODES NEAR THE LONG-WAVELENGTH EDGE

The spectral dependence of the photoemission of hot electrons across a metal silicide-silicon Schottky barrier at photon energies comparable to the barrier height is investigated. An expression for the spectral dependence of the photoemission quantum efficiency is obtained in the diffusion approximation using the Green's function formalism for diff erent values of the ratio between the layer thickness (d) and the elas tic (L-p) and inelastic (L-e) mean free paths for hot electrons. A str ong influence of the value of L-e/d on the increase in amplitude and t he form of the spectral dependence of the quantum efficiency, which de viates significantly from the Fowler dependence at increased quantum e fficiencies, has been observed. Satisfactory agreement between the the oretical and experimental spectral dependences of the quantum efficien cy is demonstrated for the silicides of Pt, Co, and Ge, making it poss ible to experimentally evaluate L-e and to optimize the technology for fabricating Schottky barriers-for infrared detectors in some cases. T he reasons for the anomalously sharp increase in the photoemission of hot electrons with increasing energy of the exciting quantum at energi es close to the potential energy of the Schottky barrier are discussed . (C) 1997 American Institute of Physics.