Si surface cleaning and epitaxial growth of GaAs on Si by electron cyclotron resonance plasma-excited molecular-beam-epitaxy at low temperatures

This paper reports Si surface cleaning prior to growth and successive epitaxial growth of GaAs on Si carried out at low temperatures by ECR plasma-excited MBE. The oxide on Si surface was removed effectively by hydrogen plasma exposure even at temperatures as low as 400 degrees C. GaAs was epitaxially grown on Si at temperatures as low as 400 degrees C using AsH3 plasma and metallic Ga. At 500 degrees C and above, single-domain GaAs was grown on double-domain Si without using a two-stem growth method. A SIMS profile revealed that no pile-up of either carbon or oxygen at the hetero-interface treated by hydrogen plasma exposure at 630 degrees C, which indicates a much cleaner interface in comparison with that of typical MOCVD-grown GaAs on Si heat-treated at 1000 degrees C. Insertion of a buffer layer grown at lower temperature with higher microwave power is effective for reducing stress without decreasing crystal quality. Using this technique, 6.6 μm thick GaAs was grown at 630 degrees C without introducing any cracks. Estimated stress of this layer is 1.5 x 109 dyn/cm2 and double-crystal x-ray diffraction measurement has shown the FWHM of (400) peak to be 190 arcsec