SURFACTANT-MEDIATED EPITAXY OF GE ON SI(111) - THE ROLE OF KINETICS AND CHARACTERIZATION OF THE GE LAYERS

Antimony as a surfactant in Ge epitaxy on Si(111) is known to suppress islanding at a growth temperature of 600-degrees-C. We used scanning tunneling microscopy (STM) to study the growth at different temperatur es. Only in the temperature range between 550 and 620-degrees-C defect -free layer-by-layer growth is stabilized. At higher temperatures a tr ansition to islanding (Stranski-Krastanov growth) occurs. At lower tem peratures the crystal quality of the layer degrades. Together with mod el experiments of Si/Si(111) homoepitaxy these results show that three -dimensional islanding is suppressed by kinetically limited growth due to reduced diffusion length in surfactant-mediated growth. Several te chniques were used to characterize the Ge layers: x-ray diffraction wa s used to determine the residual strain (0.1%), an upper limit for Sb doping of the Ge was determined by secondary ion mass spectroscopy to n(Sb)<2X10(18)/cm3. The structural quality of the Ge films was excelle nt as analyzed by Raman spectroscopy. A STM analysis gives a lower lim it for the density of dislocations threading to the surface (n(dis)<2X 10(7)/cm).