Electrical and chemical characterization of the Schottky barrier formed between clean n-GaN(0001) surfaces and Pt, Au, and Ag

Platinum, gold, and silver formed abrupt, unreacted, smooth, and epitaxial metal-semiconductor inter-faces when deposited from the vapor onto clean, n-type GaN(0001) films. The Schottky barrier heights, determined from data acquired using x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, capacitance-voltage, and cur-rent-voltage measurements agreed to within the experimental error for each contact metal and had the values of 1.2+/-0.1, 0.9+/-0.1, and 0.6+/-0.1 eV for Pt, Au, and Ag, respectively. The band bending and the electron affinity at the clean n-GaN surface were 0.3+/-0.1 and 3.1+/-0.1 eV, respectively. The barrier height is proportional to the metal work function, indicating that the Fermi level is not pinned at the GaN surface. However, discrepancies to the Schottky-Mott model were found as evidenced by a proportionality factor of 0.44 between the work function of the metal and the resulting Schottky barrier height. The sum of these discrepancies constitute the interface dipole contributions to the Schottky barrier height which were measured to be similar to1.4, 1.3, and 0.7 eV for Pt, Au, and Ag, respectively. (C) 2003 American Institute of Physics.