Effect of gas adsorption on the surface structure of β-Ga2O3 studied by XPS and conductivity measurements

In this work the mechanism of oxygen adsorption on n-type β-Ga2O3 oxide semiconductor—examined in large temperature range—is discussed based on the results of XPS and electric conductivity measurements. On one hand the effect of the adsorbed charged particles was investigated on the conductivity of the semiconductor layer, while on the other hand on the core level binding energy of oxygen and gallium. According to the former SIMS (Secondary Ion Mass Spectrometry) results the potential barrier of the depletion layer caused by the adsorbed negative ions on the surface is so high that it hinders the formation of negative secondary ions in the 450–650°C temperature range. The present results suggest the dominance of O− ion adsorption compared with that of O2−ions. The adsorption properties of β-Ga2O3 were also examined at lower temperatures (20–200°C).