CYCLOTRON EFFECTIVE-MASS OF HOLES IN SI1-XGEX SI QUANTUM-WELLS - STRAIN AND NONPARABOLICITY EFFECTS/

The Ge-composition dependence of cyclotron effective mass of quasi-two -dimensional holes in strained Si1-xGex/Si quantum well structures has been investigated by far-infrared magneto-optical spectroscopy at low temperatures and high magnetic fields up to 23 T. The in-plane effect ive mass determined from cyclotron resonance energies is much less tha n that of unstrained Si1-xGex alloys and decreases systematically from 0.40m(e) to 0.29m(e) as the Ge composition increases from x = 0.13 to x = 0.37, indicating the importance of the strain effect on the valen ce-band structure. The nonparabolicity correction is significant in ex plaining the discrepancy between the measured values and the calculate d band-edge masses.