Published in Appl. Phys. Lett. 89, 171920 (2006).

Electronic States of Oxidized GaN(0001) Surfaces

Y. Dong (a), R. M. Feenstra (a), and J. E. Northrup (b)
(a) Dept. Physics, Carnegie Mellon University, Pittsburgh, PA 15213
(b) Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA 94304


The structure and electronic properties of oxidized (0001) surfaces of GaN grown by plasma-assisted molecular beam epitaxy are investigated by scanning tunneling microscopy/spectroscopy, Auger electron spectroscopy, and first-principles theory. For oxygen exposure at room temperature an amorphous gallium oxide layer is found to form, resulting in a distribution of midgap electronic states extending out from the GaN valence band edge. The influence of these states on the electron concentration in buried AlGaN/GaN heterojunctions is discussed.

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