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Intra-valence-band mixing in strain-compensated SiGe quantum wells

S. Tsujino·A. Borak·C. Falub·T. Fromherz·L. Diehl·H. Sigg·D. Gruetzmacher
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Abstract

We explore the midinfrared absorption of strain-compensated p-Si0.2Ge0.8/Si quantum wells for various well thicknesses and temperatures. Owing to the large band offset due to the large bi-axial strain contrast between the wells and barriers, the intersubband transitions energies from the ground state to the excited heavy hole (hh), light hole (lh) and split-off hole (so) states are resolved to ~0.5 eV. When hh2 is within ~30 meV of lh1 or so1 a partial transfer of the hh1-hh2 oscillator strength to the hh1-lh1 or hh1-so1 transitions is observed, which is otherwise forbidden for light polarized perpendicular to the plane of the wells. This is a clear sign of mixing between the hh and lh or so-states. A large temperature induced broadening of hh2 peak is observed for narrow wells indicating a non-parabolic dispersion of the hh2 states due to the mixing with the lh/so continuum. We found that the 6-band k.p theory gives a quantitative account of the observations. A possible role of many-body effects in the temperatureinduced negative peak shift is discussed.

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S. Tsujino, A. Borak, C. Falub, T. Fromherz, L. Diehl, H. Sigg, D. Gruetzmacher. 2005-05-13. Intra-valence-band mixing in strain-compensated SiGe quantum wells. https://doi.org/10.1103/physrevb.72.153315

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