INVESTIGATION OF SI-SUBSTRATE PREPARATION FOR GAAS-ON-SI MBE GROWTH

Auger electron spectroscopy (AES) and material characterization techni ques have been used to investigate different chemical treatments for t he preparation of Si substrates for GaAs-on-Si molecular beam epitaxy (MBE). The need for a Si surface passivating oxide is justified and th ree different oxidizing solutions are compared for substrate cleanline ss and oxide volatility. It is shown that the SC2 solution HCI:H2O2:H2 O (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 a lso be used as ''EPI-ready'' substrates within some time after manufac turing.