MICROSTRUCTURAL DEVELOPMENT AND OPTICAL-PROPERTIES OF EPITAXIAL GE1-XCX ALLOYS ON SI(100)

We report on the microstructural development and optical properties of epitaxial Ge1-xCx alloys (0<x<0.1) grown on Si(100) by low-temperatur e (200 degrees 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 tha t less than 1% C may have been substitutionally incorporated. Spectros copic ellipsometry measurements of the films' optical constants show s mall systematic changes with increasing C concentration. These changes occur primarily near 2 eV, the E(1) critical point in Ge. No new feat ures attributable to Ce-C vibrational modes could be identified using Raman spectroscopy. (C) 1995 American Institute of Physics.