Properties of Metal-Semiconductor Interfaces Formed on n-Type GaN

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Abstract
Properties of metal/GaN Schottky diodes formed by the conventional vacuum deposition process and a novel in situ electrochemical process are investigated by detailed I–V, C–V and X-ray photoelectron spectroscopy (XPS) measurements with a special focus on the correlation between the contact formation process and the behavior of Schottky barrier height. Schottky diodes formed by vacuum deposition pretreated with a warm NH4OH solution showed nearly ideal thermionic emission I–V characteristics with Schottky barrier height (SBH) values weakly dependent on metal work function with the slope factor of about 0.1. On the other hand, Schottky diodes formed by the in situ electrochemical process also showed high-quality nearly ideal thermionic emission I–V characteristics, but they realized strongly metal-work-function-dependent SBH values. The slope factor, S, was as large as 0.49. These results could not be explained by the recently proposed formula based on the metal induced gap state (MIGS) model. They are explained here from the viewpoint of the disorder induced gap state (DIGS) model.