CYCLOTRON-RESONANCE MEASUREMENTS OF SI SIGE 2-DIMENSIONAL ELECTRON GASES WITH DIFFERING STRAIN/

Far-infrared cyclotron resonance measurements have been used to invest igate the effective mass in the strained silicon channels of modulatio n-doped, two-dimensional electron gases grown on relaxed Si1-xGex. By using a range of Ge fractions x, the effect of strain was investigated . Consistent results were obtained when the resonance positions were f itted to a model for zero-dimensional confinement, yielding mapproxim ate to 0.196 m(e) for most samples. The use of this formula was justif ied by invoking electron localization due to a disorder potential. The observed confinement effect was strongest in two samples where the Si channel was partially relaxed, suggesting this to be a possible mecha nism. Qualitatively different results were obtained for a sample with a high background concentration of donor impurities, indicating that t he type of disorder present can affect the nature of the resonances. ( C) 1998 American Vacuum Society.