The theory of hot-electron photoemission in Schottky-barrier IR detectors

Two semiclassical ballistic transport models for thin films developed in 1971 treat the problem of "hot-electron" internal photoemission in Schottky-barrier diode IR detectors. Both formulations take into account multiple scattering from the surfaces as well as hot-electron-phonon and hot-electron-cold-electron collisions in the bulk. The models are compared for the case of uniform absorption and one of the models is then extended. The extensions incorporate the effect on internal quantum yield of small energy losses from electron-phonon collisions. Also, it is no longer assumed that the fraction removed by capture is small which insures that the yield cannot exceed the theoretical upper limit. The results are illustrated by Fowler plots over a range of scattering parameters and thicknesses germane to Schottky diodes of current interest, PtSi/Si and Pd2Si/Si. The main new features of the plots include curvature for photon energies close to the barrier energy due to phonon collision thermalization and roll-off at higher excitation energies whenever the yield is comparable in magnitude to the theoretical limit. The model is in good agreement with earlier Monte Carlo computations.