The Si epitaxial films are grown on Si （100） substrates using pure Si2H6 as a gas source using ultrahigh vacuum chemical vapour deposition technology. The values of growth temperature Tg are 650 ℃, 700 ℃, 730 ℃, 750 ℃, and 800 ℃. Growth mode changes from island mode to step-flow mode with Tg increasing from 650 ℃ to 700℃. Rippled surface morphologies are observed at Tg = 700 ℃, 730 ℃, and 800℃, but disappear when Tg = 750℃. A model is presented to explain the formation and the disappearance of the ripples by considering the stability of the step-flow growth.
Epitaxial Ge1-xSnx alloys are grown separately on a Ge-buffer/Si（100） substrate and directly on a Si（100） substrate by molecular beam epitaxy （MBE） at low temperature. In the case of the Ge buffer/Si（100） substrate, a high crystalline quality strained Ge0.97Sn0.03 alloy is grown, with a Xmin value of 6.7% measured by channeling and random Rutherford baekscattering spectrometry （RBS）, and a surface root-mean-square （RMS） roughness of 1.568 nm obtained by atomic force microscopy （AFM）. In the case of the Si（100） substrate, strain-relaxed Ge0.97Sn0.03 alloys are epitaxially grown at 150℃-300℃, with the degree of strain relaxation being more than 96%. The X-ray diffraction （XRD） and AFM measurements demonstrate that the alloys each have a good crystalline quality and a relatively flat surface. The predominant defects accommodating the large misfit are Lomer edge dislocations at the interface, which are parallel to the interface plane and should not degrade electrical properties and device performance.
