Investigation of Si-substrate preparation for GaAs-on-Si MBE growth

Auger electron spectroscopy (AES) and material characterization techniques have been used to investigate different chemical treatments for the preparation of Si substrates for GaAs-on-Si molecular beam epitaxy (MBE). The need for a Si surface passivating oxide is justified and three different oxidizing solutions are compared for substrate cleanliness and oxide volatility. It is shown that the SC2 solution HCI:H2O2:H2O (1:1:6) at 75 degrees C is an appropriate treatment for the final Si cleaning step, since it results to a very volatile oxide that can be desorbed at 750 degrees C, without compromising Si surface cleanliness and GaAs purity. Si wafers with optimized preparation/packaging may also be used as ''EPI-ready'' substrates within some time after manufacturing.