Cyclotron effective mass of holes in Si1−xGex/Si quantum wells: Strain and nonparabolicity effects

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Abstract
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 effective mass determined from cyclotron resonance energies is much less than that of unstrained Si1−xGex alloys and decreases systematically from 0.40me to 0.29me as the Ge composition increases from x=0.13 to x=0.37, indicating the importance of the strain effect on the valence‐band structure. The nonparabolicity correction is significant in explaining the discrepancy between the measured values and the calculated band‐edge masses.