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Diffusion of Ge below the Si(100) surface: theory and experiment
1Department of Physics, Box 351560, University of Washington, Seattle, Washington 98195-1560 and Department of Chemistry, Box 351700, University of Washington, Seattle, Washington 98195-1700, USA.
Physical Review Letters
|October 6, 2000
Summary
Germanium (Ge) diffuses into silicon (Si) subsurface layers even at low temperatures. This diffusion behavior, particularly in n-type doped silicon, could enable sharper silicon-germanium interfaces.
Area of Science:
- Materials Science
- Surface Science
- Solid-State Physics
Background:
- Understanding the diffusion of germanium (Ge) into silicon (Si) is crucial for fabricating advanced semiconductor devices.
- Subsurface diffusion of Ge in Si(100) influences the properties of Si/Ge heterostructures.
Purpose of the Study:
- To investigate the diffusion of Ge into the subsurface layers of Si(100).
- To determine the equilibrium Ge subsurface distributions and the energy pathways involved.
- To explore the effect of doping on Ge diffusion and Si/Ge interface sharpness.
Main Methods:
- Experimental measurements using Auger electron diffraction.
- Theoretical predictions employing density functional theory (DFT).
Main Results:
- Germanium was observed in the fourth layer of Si(100) after submonolayer growth at temperatures as low as 500°C.
- DFT predictions of equilibrium Ge subsurface distributions align with experimental findings.
- A low energy pathway for Ge diffusion was identified, attributed to low interstitial formation energy in deeper Si layers.
Conclusions:
- Ge diffusion into subsurface Si layers occurs readily, even at moderate temperatures.
- The formation energy of Ge interstitials is significantly influenced by doping.
- N-type doping shows potential for creating sharper Si/Ge interfaces due to altered formation energies.