Abstract
We develop a unified kinetic model for surface segregation during vapor phase growth that concisely and quantitatively describes the observed behavior in silicon-based systems. A simple analytic function for the segregation length is derived by treating terrace-mediated and step-edge-mediated mechanisms in parallel. The predicted behavior of this parameter is examined through its temperature, flux, and terrace length dependence. Six distinct temperature regimes are predicted for the segregation length that depend on the relative segregation energies and activation barriers of the two mechanisms. The model is compared to reported behavior of Sb and P in Si(001) and excellent agreement is obtained using realistic energies and preexponential factors. The model accounts for the experimentally observed anomalous low-temperature segregation of Sb as a consequence of the competition between step-edge-mediated segregation, dominant at low temperatures, and terrace-mediated segregation, dominant at higher temperatures. The generalized treatment of segregation mechanisms in the model makes it applicable to other segregating systems, including metals and III-V semiconductors.
Highlights
Recent advances in thin-film growth technology to improve density, speed, or other device properties require accurate control of impurities and dopants at small length scales
We develop a unified kinetic model for surface segregation during vapor phase growth that concisely and quantitatively describes the observed behavior in silicon-based systems
Six distinct temperature regimes are predicted for the segregation length that depend on the relative segregation energies and activation barriers of the two mechanisms
Summary
Recent advances in thin-film growth technology to improve density, speed, or other device properties require accurate control of impurities and dopants at small length scales. Complex architectures such as delta-doping[1,2] or band-gap engineering[3] for quantum well devices[4,5,6] or spintronic applications[7,8] require sharp heterostructures in semiconductors. The system is considered to be in a kinetically limited segregation regime In this case, the segregation is determined by the kinetics of moving impurity atoms, and the relatively low mobilities cause them to become trapped in the growing film. We demonstrate the effectiveness of the model by reproducing, for the first time, the measured temperature and growth rate dependence for Sb and P in Si001͒
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