A first principle study on oxygen adsorption and incorporation on the (1 0 0) surface of [0 0 1]-oriented GaN nanowires

Oxygen adsorption and incorporation on the (1 0 0) surface of [0 0 1]-oriented GaN nanowires are investigated through first principle calculations. Results indicate that oxygen adsorption configurations are much more stable than oxygen incorporation. With increasing oxygen coverage, the surface of oxygen adsorption and incorporation become more stable and unstable, respectively. Besides, significant changes of surface structure occur after oxidization of the GaN nanowire surface, including changes in the thickness of the topmost bilayer and the distance between layers. Relaxation of the surface structure becomes more prominent with increasing oxygen coverage for adsorption cases. Compared with adsorption, the effects of incorporation on surface structures are more obvious. Furthermore, by comparison of band structures of clean surfaces and oxidized surfaces, both oxygen adsorption and incorporation will hinder the escape of photoelectrons due to the increase of the work function. Ultimately, calculations of Mulliken charge distribution and bond population suggest that oxygen impurities can obtain electrons from surface gallium and nitrogen atoms. The bond population of Ga–O for adsorption cases are larger than Ga–N, while that of incorporation cases is lower than Ga–N. All these calculations indicate that oxidization has significant impacts on the surface characteristics of GaN nanowires. Surface oxidization is harmful to the photoemission of optoelectronic devices fabricated by GaN nanowires. These results may contribute to the removal of surface oxides of GaN nanowires, but require further verification by experimental observation. (paper)