Atomic layer epitaxy of Si on Ge(100): Direct recoiling studies of film morphology

Two Si atomic layer epitaxy schemes based on Cl/H exchange chemistry are compared by deposition of Si on Ge(100). Time-of-flight direct recoiling and reflection high-energy electron diffraction are used to characterize the very thin Si layers. It is shown that alternating exposure to SiCl2H2 and atomic hydrogen deposits Si in a process that is self-limiting. Growth of Si by this method results in either alloy formation or Si island growth as low as 465 °C on Ge(100), which prohibits a simple measurement of Si thickness/cycle. In contrast, alternating exposure to Si2Cl6 and Si2H6 below 500 °C results in Si deposition with uniform thickness. Plots of direct recoil intensity versus incident angle (with respect to the surface plane) are a sensitive probe of the thin layer morphology.