Microstructural development and optical properties of epitaxial Ge < inf> 1-x C < inf> x alloys on Si(100)

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We report on the microstructural development and optical properties of epitaxial Ge1-xCx alloys (0 < x < 0.1) grown on Si(100) by low-temperature (200°C) molecular-beam epitaxy. Films with C concentrations below 2%-3% grow in 2D layers, while films with C higher than 5% form 3D islands after initial layer growth. X-ray-diffraction indicates that less than 1% C may have been substitutionally incorporated. Spectroscopic ellipsometry measurements of the films' optical constants show small systematic changes with increasing C concentration. These changes occur primarily near 2 eV, the E1 critical point in Ge. No new features attributable to Ge-C vibrational modes could be identified using Raman spectroscopy. © 1996 American Institute of Physics.

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Applied Physics Letters