Heavy ion backscattering spectroscopy (HIBS) analysis of gallium arsenide diffusion into barium fluoride layers grown by molecular beam epitaxy

Heavy Ion Backscattering Spectroscopy (HIBS) using 12 MeV 12C ions was used to examine GaAs (1 0 0) and GaAs (1 1 1) layers grown by Molecular Beam Epitaxy (MBE) on BaF 2 (1 0 0) and BaF 2 (1 1 1) layers, respectively. HIBS was the only available technique able to verify the Ga As ratio in these samples because X-ray Photoelectron Spectroscopy (XPS) is too surface sensitive for this task and the lighter ions used in Rutherford Backscattering Spectroscopy (RBS) cannot resolve the Ga and As signals. A modified RBS analysis program was used to analyze the HIBS spectra. Using the stopping power data of Ziegler et al., the HIBS analysis overestimated the thickness of a BaF 2 layer by about 14% when compared to RBS analysis of the same layer. HIBS was able to resolve the Ga and As peaks, as well as the two isotopes of Ga. This enhanced mass resolution made the determination of the GaAs layer stoichiometry possible, and introduced spectral features that aided in fitting HIBS simulation spectra to the data points. HIBS analysis of GaAs/BaF 2/Si heteroepitaxies also showed diffusion of Ga and As into BaF 2. This diffusion is temperature dependent and therefore subject to control. The information gathered from the HIBS analysis was used to confirm information obtained by in situ MBE diagnostic techniques, and in the case of the diffusion studies, provided information that was not available by those surface sensitive techniques.