Surface roughening of tensilely strained Si1−x−yGexCy films grown by ultrahigh vacuum chemical vapor deposition

Using in situ reflection high-energy electron diffraction, we have studied the surface roughening of SiGeC that occurs in ultrahigh vacuum chemical vapor deposition under certain growth conditions. For a given SiH3CH3 fraction in the gas phase, high growth rates and low temperatures are found to be favorable to obtain smooth surfaces. Roughening is accompanied by a dramatic decrease of the substitutional C content. According to these observations, we propose a model of surface roughening based on the formation of carboneous complexes on the film surface, limited by the growth rate and the diffusion length of C adatoms. From that, a critical ratio between the growth rate and the C diffusion coefficient was assumed. Its temperature dependence was determined. The activation energy of C adatoms diffusion was found to be close to the well known value for hydrogen desorption.

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