<title>Fundamental studies of Schottkybarrier infrared detectors by ballistic-electron-emission microscopy</title>

Abstract

Here, we report on our studies of ballistic electron transport across metal layers and metal/semiconductor interfaces using ballistic-electron-emission microscopy (BEEM). This new technique, which uses a scanning tunneling microscope to inject electrons with a controlled energy into a thin metal film, allows measurements (with spatial resolution approaching 1 nm) of (1) the local Schottky barrier height, (2) ballistic mean free paths of energetic electrons (or holes), and (3) transmission probability of hot carriers across the metal/semiconductor interface. We have measured the attenuation length of hot electrons (1.5 eV above the Fermi level) in PtSi to be approximately 4 nm. This should be compared with an attenuation length of 13 nm for similar energy electrons in Au layers. BEEM images of the Au/Si interface show features on a very small length scale suggesting that the inelastic mean free path of electrons in Au is close to the attenuation length. The SB height (as determined by BEEM) is 0.87 eV in good agreement with optical measurements. We have also used BEEM to observe the sharp onset of inelastic scattering mechanisms in Au/Si and in PtSi/Si. It is our belief that these studies of ballistic carrier transport will allow a fundamental determination of how to achieve higher quantum efficiencies in SBIRDs.