REFLECTANCE ANISOTROPY AND REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION INTENSITY OSCILLATIONS DURING GAS-SOURCE MOLECULAR-BEAM EPITAXY GROWTH OF SI AND SIGE ON SI(001)

Dynamic reflectance anisotropy (RA) and reflection high-energy electro n diffraction (RHEED) intensity measurements were used to study the ep itaxial growth of Si and SiGe on Si(001) using gas source molecular be am epitaxy (GSMBE). Oscillatory behaviour in the RA response was obser ved using a HeNe laser at 1.96 eV during growth of Si and SiGe over a wide range of temperatures. Whilst the surface retains a two domain (1 x 2)+(2 x 1) reconstruction during growth, the period of the RA oscil lations corresponds to the time required for the growth of two monolay ers (ML). Simultaneous RHEED intensity oscillations observed along the [110] azimuth indicate that the growth proceeds in a hit mode and tha t the frequency observed is twice that of the RA oscillations. This os cillatory behaviour of the RA response is explained in terms of the va rying dimer concentrations along the two orthogonal (110) directions a nd hence the relative coverages of the two domains. Comparisons are ma de between the RHEED and RA oscillations to explain the significance o f the RA response.