Kelvin Probe Force Microscopy Study of the Electrostatic System of the Crystal Surface of AuNi/GaN Schottky Diodes

摘要

Using atomic-force-microscopy investigations of the electrostatic system of the crystal surface of AuNi/n-n(+)-GaN planar Schottky diodes, it is shown that the electron work function for the surface of metal Schottky contacts depends on their linear size (diameter D). At D > 120 mu m, the work function of the central contact region approaches the work function e phi(Au) approximate to 5.40 eV of a continuous metallic gold film. A decrease in the diameter leads to a decrease in the work function to 5.34 eV at D = 120 mu m, 5.21 eV at D = 40 mu m, 5.18 eV at D = 10 mu m, and 5.14 eV at D = 5 mu m. The observed decrease in the work function with diameter is related to the increasing influence of the built-in periphery electrostatic field E-l, which is determined by the area and perimeter of the Schottky contact. The fundamental differences between the thermodynamic and electrostatic systems of TiAlNiAu/n(+)-GaN ohmic contacts, in contrast to analogous AuNi/n-GaN Schottky systems, are indicative of the absence of a Schottky barrier in them and the decisive role of the thermionic transport of mobile carriers.