Ballistic-electron-emission microscopy of (100)CoGa/n-type GaAs interfaces grown by molecular beam epitaxy

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Abstract
A scanning tunneling microscope (STM) was used for the first time to investigate the (100)CoGa/GaAs interfaces grown by molecular beam epitaxy. The surface image indicates a vertical variation of about 7.5 Å with some domains of dimensions of about 170 Å. Furthermore, ballistic‐electron‐emission‐microscopy spectra of this metal/semiconductor interface show two turn‐on voltages, which account for the change of transmission probabilities for electrons with energies above the L minima and X minima of GaAs, respectively. The transmission into the X valleys of GaAs is found to be relatively stronger than that into the L valleys. This is explained by the CoGa band structure and the conservation of energy and transverse momentum for ballistically injected electrons. So far no ballistic electron current flowing into the Γ valley has been observed. For this reason, Schottky barrier height and its spatial variation measured by STM were not directly from the anticipated turn‐on voltage at the Γ minimum, but instead, from the thresholds corresponding to transmission into higher valleys.