IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Semiconductors Wednesday Sessions
       Session SC+SS+EL-WeA

Paper SC+SS+EL-WeA6
Ex Situ Removal of Carbon and Oxygen from a Gallium Nitride (0001) Surface

Wednesday, October 31, 2001, 3:40 pm, Room 111

Session: Chemistry of Semiconductor Etching & Cleaning
Presenter: F. Machuca, Stanford University
Authors: F. Machuca, Stanford University
Z. Liu, Stanford University
Y Sun, Stanford University
R.F.W. Pease, Stanford University
W.E. Spicer, Stanford University
P. Pianetta, SSRL and Stanford University
Correspondent: Click to Email
We report on a chemical cleaning study of gallium nitride (GaN) using synchrotron radiation to probe the electronic structure of the semiconductor surface and the adsorbed impurities. We study sulfuric peroxide and sulfuric water chemistries for carbon and oxygen removal using the surface sensitive core level information using XPS. We report that a sulfuric peroxide wet treatment followed by a vacuum anneal at 700C reduces C and O concentrations to a few percent of a monolayer. Moreover, this is the first study achieving an atomically clean GaN surface well below the decomposition temperature by 200C. This is a direct result of a weaker form of carbon being chemisorbed to the GaN surface after the peroxide treatment and that is subsequently thermally desorbed. The chemical form is predominantly an oxide of carbon. Whereas the sulfuric water treatment leaves a residual refractive carbon on the surface of GaN in the form of hydrocarbons. These hydrocarbons persist up to the maximum annealing temperature of 740C tested. We also show that by treating the GaN surface with an aggressive oxidizing chemistry like sulfuric peroxide, there is only near monolayer coverages of oxygen. This is direct evidence for the existence of a suboxide on the GaN surface and demonstrates GaN (0001) is not an active surface for bulk oxidation. We also test the effectiveness of the annealing ambient during the thermal desorption portion of the cleaning by comparing vacuum to ammonia annealing. Our findings indicate ammonia is ineffective in aiding thermal desorption of C and O at temperatures at or below 740C, contrary to other reports. Lastly, we offer evidence for a novel oxynitride species on the GaN surface.