Fermi level pinning by metal Schottky contacts on n type GaAs

Abstract

The Schottky barrier heights, as determined by current–voltage and capacitance–voltage, of thirty six metals which were fabricated by following the same cleaning procedure and using the same high quality organometallic vapour phase epitaxy (OMVPE) grown (100) n type GaAs material, are presented. It was found that there exists no linear relationship between Schottky barrier height and metal work function as is suggested by the Schottky–Mott theory, if all the above-mentioned metals are taken into account. Similar results were obtained if the metal work function was replaced by the Pauling or Miedema electronegativities. In contrast, if only a selected group of metals is chosen, and more specifically those with high melting points which were deposited by means of an electron gun, a linear relationship does exist between Schottky barrier height and metal work function. From this linear dependency, the density of states was determined to be about 6 × 1013 eV cm−2 and the pinning position of the Fermi level as 0.55 eV.