MEASUREMENTS OF ALLOY COMPOSITION AND STRAIN IN THIN GEXSI1-X LAYERS

The utility of Raman spectroscopy for the simultaneous determination o f composition and strain in thin GexSi1-x layers has been investigated . Using data from the literature and new data for the strain shift of the Si-Si phonon mode presented here, we show how Raman spectra provid e several different means of measuring composition and strain in sampl es as thin as 200 angstrom. We demonstrate that for largely relaxed la yers with compositions near x = 0.30, Raman scattering can measure the composition, x, with an accuracy of +/-0.015 and the strain, epsilon, with an accuracy +/-0.0025. The accuracy of the alloy composition obt ained from Raman spectra is comparable or, in the case of very thin la yers, superior to that measured by other techniques such as x-ray diff raction, electron microprobe, and Auger electron spectroscopy.