ADAPTIVE TEMPERATURE PROGRAM ALE OF SI1-XGEX SI HETEROSTRUCTURES FROMSI2H6/GE2H6/

We describe a thermally-driven atomic layer epitaxy technique that all ows submonolayer thickness control over the growth of planar heterostr uctures. Our temperature programmed desorption measurements show that the temperature required to desorb essentially all passivating hydroge n species decreases sharply with increasing Ge coverage (99.9% removed after 5 min at 730 K on Si and 5 min at 580 K on Ge). In adaptive tem perature program-atomic layer epitaxy, this coverage dependence of the hydrogen desorption rate is exploited to supply sufficient heat to re activate the surface, while minimizing the impact of other thermally a ctivated processes, such as surface segregation and island formation t hat are also driven by high concentrations of germanium. Temperature p rogrammed desorption, Auger electron spectroscopy and cross-section tr ansmission electron microscopy indicate that Ge interface segregation is rapid for such growth conditions, but limited in spatial extent to several monolayers. The onset of three-dimensional island growth was o bserved only for concentrated (> 20%-Ge) alloy films.