Hard X-ray photoelectron spectroscopy investigation of annealing effects on buried oxide in GaAs/Si junctions by surface-activated bonding

Hard X-ray photoelectron spectroscopy measurements are performed on approximate to 10-nm-thick GaAs film/Si substrate junctions fabricated by the surface activated bonding and selective wet etching. The chemical shifts of Ga-O and As-O signals in Ga 2p(3/2) and As 2p(3/2) core spectra indicate that oxides are formed in a part of GaAs films neighboring GaAs/Si interfaces due to the surface activation process. Analyses of Ga-O and As-O signals show that the thickness of such buried oxides is decreased due to a post-bonding annealing at temperatures up to 400 degrees C. This means that the electrical properties of bonding interfaces, which are in the meta-stable states, are improved by the annealing. The thickness of oxides is different from that of amorphous-like transition layers at the GaAs/Si interfaces observed by transmission electron microscopy.