Si(001) growth dynamics during Si GSMBE from disilane

Abstract

Reflection high-energy electron diffraction (RHEED) intensity oscillations have been used to monitor the growth of Si(001) during gas source molecular beam epitaxy (Si-GSMBE) from disilane. Oscillations are easily obtained on well prepared surfaces on which a buffer layer has been grown. Oscillations of the specular beam in both the [010] and [110] azimuths have been measured as a function of temperature and disilane flow rate. Strong and damped oscillations were observed between 610 and 680°C in the two-dimensional growth regime. At higher temperatures growth by step propagation dominated, while at lower temperatures growth became three-dimensional (3D) and consequently oscillations were weak or absent. Oscillations of the fractional order and specular beams in the [110] azimuths indicate that growth occurs in a monolayer rather than a bilayer fashion, and the alternating intensity of sequential oscillations in the specularly reflected beam in the [110] azimuth may be indicative of the relative step density in the two orthogonal directions. Growth rates, as determined from the oscillations, are found to be independent of incident beam flux at substrate temperatures below 600°C, but become dependent at higher temperatures. An Arrhenius plot indicates an activation energy ( E A ) of 40.7 kcal/mol in the low temperature regime ( T < 600° C) and an apparent E A dependence on disilane flux in the high temperature regime.