Physiochemical Effects of Heating Gold Thin Films on Gallium Arsenide

The physiochemical effects of heating gold thin films on GaAs, namely, the arsenic evolution, gold-to-silver color transition, and microstructural changes, were investigated by in situ mass spectrometric evolved gas analysis and scanning electron microscopy. The gold-to-silver color transition was found to occur after a small amount of arsenic evolution. The transition temperature increased with increasing air pressure and gold film thickness. The relative quantities of arsenic species evolved followed the order As4 > Ase> As > As3. We observed a new microstructure consisting of interconnected irregularly shaped protrusions which appeared after a small amount of arsenic evolution and changed to the previously reported microstructure of aligned rectangular protrusions near the completion of the arsenic evolution.