The Effect of Surface Cleaning by Wet Treatments and Ultra High Vacuum Annealing for Ohmic Contact Formation of P-Type GaN

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Abstract
The effect of surface cleaning techniques on the properties of the metal/p-GaN contacts has been studied using X-ray photoelectron spectroscopy (XPS) and I–V measurements. It has been clarified that the contact resistance strongly depends on the amount of the surface residues such as oxygen and carbon just before the electrode deposition. We have also found that the annealing in ultra high vacuum (UHV) is effective to reduce the residues. It has turned out that the combination of the hydrochloric acid and sulfuric acid hydrogen peroxide mixtures cleaning followed by the UHV annealing is promising for the improvement in the contact characteristics.