An XPS study of GaN thin films on GaAs

Abstract

The energies of photoelectron and Auger lines of gallium and nitrogen in GaN thin films obtained by reactive sputtering are derived From previous RBS investigations, such films were found to be stoichiometric in the bulk. The XPS surface analysis of the films gives a chemical content of -20% gallium oxide. Depth profiling of GaN/GaAs samples is then performed by Ar+ (2 keV) sputter-etching. The Ga L3M,,,M,,, Auger line shows a partial dissociation of GaN by preferential sputtering of nitrogen and the production of metallic gallium The Ga 3d and Ga 2p photoelectron lines, having different escape depths, give the same result. The etching rate is high: the GaN sputtering yield, which is almost the same as that for Ga, is found to be -8. The gallium oxide component disappears for depths larger than 10 nm: it is concluded that the surface gallium oxide is probably due to the partial oxidation of GaN films in atmospheric air.

X-Ray Photoelectron Spectroscopic Investigation of the GaAs Nitridation Mechanism with an ECR Plasma Source

“…The efficiency of this second nitridation step is improved since about one third of the received nitrogen is incorporated as b-GaN. The 0.5 eV separation of the gallium core levels is in agreement with the BE difference measured in a GaN/GaAs heterostructure by Carin et al [12]. Similarly, the N 1s level found at 396 eV below the valence band maximum is expected at a lower binding energy in Ga±N than in any other possible bonding states such as N±N or N±As.…”

Photoemission spectroscopy studies of the surface of GaN films grown by vapor phase epitaxy

“…[6][7][8][9][10][11] They have been compared with optical measurements 12 and limited photoemission spectroscopy measurements. [13][14][15][16][17][18][19] There have as yet been no systematic measurements on surfaces of GaN that are believed to be clean. Different groups do not even agree on the binding energy of Ga͑3d͒ core levels.…”

“…Different groups do not even agree on the binding energy of Ga͑3d͒ core levels. [13][14][15][16][17][18][19] In this Letter, we report a study of the surface of GaN films grown by halide vapor phase epitaxy ͑HVPE͒ using synchrotron radiation angle-integrated photoemission spectroscopy. Our measurements indicate that the variability in results obtained by different groups is related to contaminants on and the stoichiometry of the surface of GaN.…”

Improved Heteroepitaxial MBE GaN Growth with a Ga Metal Buffer Layer

“…From the measured photoemission spectra with 130 eV photon energy, two peaks representing Ga 3d can be resolved, as shown in Figure 3(a). The peak at lower kinetic energy corresponds to Ga 3d in GaN, and the higher kinetic energy peak corresponds to Ga 3d in metallic Ga [7]. Evidently, excess Ga remains in the nitrided Ga layers in metallic form.…”