Adaptive temperature program ALE of Si1 − xGex/Si heterostructures from Si2H6/Ge2H6

We describe a thermally-driven atomic layer epitaxy technique that allows submonolayer thickness control over the growth of planar heterostructures. Our temperature programmed desorption measurements show that the temperature required to desorb essentially all passivating hydrogen 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 temperature program-atomic layer epitaxy, this coverage dependence of the hydrogen desorption rate is exploited to supply sufficient heat to reactivate the surface, while minimizing the impact of other thermally activated processes, such as surface segregation and island formation that are also driven by high concentrations of germanium. Temperature programmed desorption, Auger electron spectroscopy and cross-section transmission 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 observed only for concentrated (> 20%-Ge) alloy films.