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Observation of columnar microstructure in step-graded Si1-xGex/Si films using high-resolution X-ray microdiffraction
D E Eastman1, C B Stagarescu, G Xu
1James Franck Institute, University of Chicago, 5640 S. Ellis Avenue, Chicago, Illinois 60637, USA.
Physical Review Letters
|April 17, 2002
Summary
High-resolution X-ray microdiffraction revealed a columnar microstructure in silicon-germanium/silicon (SiGe/Si) films. This structure consists of tilted micrograins, crucial for understanding material properties in advanced semiconductor devices.
Area of Science:
- Materials Science
- Solid State Physics
- Semiconductor Heterostructures
Background:
- Step-graded Si(1-x)Ge(x)/Si(001) structures are essential for semiconductor devices.
- Controlling threading dislocation density is critical for device performance.
- Understanding the microstructure is key to optimizing material properties.
Purpose of the Study:
- To determine the columnar microstructure of step-graded SiGe/Si structures.
- To investigate the relationship between microstructure and low threading dislocation densities.
- To characterize the size, orientation, and lattice spacing of microstructural features.
Main Methods:
- High angular resolution X-ray microdiffraction was employed.
- X-ray rocking curves were measured for a 3-micrometer-thick Si(0.83)Ge(0.17) film.
- Data was simulated using a Gaussian model to analyze microstructural parameters.
Main Results:
- A columnar microstructure composed of tilted rectangular micrograins was identified.
- Individual micrograins exhibited narrow angular widths (0.013-0.02 degrees).
- Local tilt angles ranged from 0.05 to 0.2 degrees, with average micrograin areas of 0.8 to 2.0 micrometers squared.
Conclusions:
- The study successfully characterized the columnar microstructure in SiGe/Si films.
- The findings provide insights into the formation of strain-relaxed layers with low defect densities.
- This detailed microstructural understanding is vital for the development of high-performance SiGe/Si-based electronic devices.
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