The Schottky barrier heights of metal contacts, including W Si0.8, Cr, Ti, Pt, and Ni, on n -type gallium nitride (GaN) with a GaN cap layer grown at low-temperature (LTG) were studied. Higher barriers can be formed by introducing LTG GaN on top of the conventional structures. The higher Schottky barrier observed in samples with the LTG GaN cap layer may be due to the facts that the high-resistivity LTG GaN layer may passivate the surface defects (pits) formed from threading dislocations or it may cause the Fermi-level pinning effect at the metal/semiconductor interface, revealing a weak dependence of Schottky barrier height on the metal work function. The measured barrier heights of the LTG GaN-capped samples were 1.02-1.13 eV.
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