GIANT VARIATION IN SCHOTTKY-BARRIER HEIGHT OBSERVED IN THE CO SI SYSTEM/

In the literature, the Schottky barrier height (SBH) of Co/Si-related interfaces consistently has been found to lie close to 0.65 eV on n-ty pe Si. This apparent insensitivity of the SBH to the phase of the sili cide and crystallographic orientation of the substrate had previously been thought to support Fermi-level pinning mechanisms. We have, howev er, through careful control Of molecular-beam epitaxy processing, grow n single crystal type B CoSi2/Si (111) layers which exhibit a giant va riation in SBH. CoSi2/Si(111) interfaces prepared by room temperature and high temperature processing exhibit n-type SBHs close to 0.7 eV an d p-type SBHs close to 0.45 eV, in good agreement with the SBHs of oth er Co/Si-related interfaces. However, CoSi2/Si (111) interfaces prepar ed by special layered growth techniques (here labeled as ''X'' interfa ces) exhibit n-type SBHs less than 0.3 eV and p-type SBHs over 0.7 eV- a difference of over 400 meV from the room temperature and high temper ature interfaces. Other CoSi2/Si (111) interfaces prepared by differen t processing conditions also often exhibit low n-type SBHs and elevate d p-type SBHs, but over a somewhat smaller range. Plan-view and high-r esolution transmission electron microscopy clearly indicated the exist ence of structural defects or inhomogeneity in the low n-type SBH samp les.