XPS analysis of the terminated‐bonding states at GaN surface after chemical and plasma treatments

In order to improve reliability and yield of gallium nitride (GaN) devices, we have developed the formation of an ultra-clean GaN surface and an interface of a passivation layer. The residue or termination materials on the GaN surface were analyzed after wet-chemical and plasma treatments. In detail, the terminated-bonding state of the GaN surface has been characterized by X-ray photoelectron spectroscopy. After conventional diluted HF treatment, the GaN surface is still terminated by oxygen. (NH4)2Sx and SiH4 plasma treatments are required for the efficient removing of oxygen-termination of the GaN surface. However, contaminants, except for nitrogen and gallium, are not removed from the GaN surface completely. For example, silicon is deposited on the GaN surface after the SiH4 plasma treatment, and atoms of sulfur are terminated on the GaN surface after the (NH4)2Sx treatment. However, we consider that their materials should be removed before the passivation film deposition. Therefore, the ultra-clean interface of the passivation layer and the GaN surface were reported in this paper. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)