Surface chemical states of heteroepitaxial nitride films on sapphire by metalorganic chemical vapor deposition

Surface chemical states of GaN, AlGaN and InGaN by metalorganic chemical vapor deposition, and the influence of different dopants are studied with X-ray Photoelectron Spectroscopy (XPS). The results show that for most of the samples the N 1s peak can be fitted with a dominant GaN peak and a small N H peak, while Ga 3d can be deconvoluted into three peaks from elemental Ga, GaN and Ga ₂O₃. Si-doping appears to have small influence on the surface chemical states of GaN while the influence of Mg-doping appears larger. In addition to a change in the component intensities, Mg-doping also causes the N 1s and Ga 3d peaks to broaden. The ternary AlGaN sample shows aluminum surface segregation, while the undoped InGaN shows indium surface deficiency.