Intersubband absorption in modulation doped p-type Si1-xGex quantum wells: theory and experiment

✍ Scribed by T. Fromherz; E. Koppensteiner; M. Helm; G. Bauer; J.F. Nützel; G. Abstreiter

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 226 KB
• Volume: 15
• Category: Article
• ISSN: 0749-6036
• DOI: 10.1006/spmi.1994.1046

✦ Synopsis

A study of intersubband infrared absorption in modulation doped p-type (\mathrm{Si} / \mathrm{SiGe}) quantum wells is presented for SiGe wells with thicknesses between (22 \AA) and (64 \AA) and (\mathrm{Ge}) contents in the range from (23 %) to (58 %). The peak positions of the absorption lines are observed between (500 \mathrm{~cm}^{-1}) and (2200 \mathrm{~cm}^{-1}). Depending on the barrier height (i.e., on the Ge content of the wells), the heavy-hole states excited by the infrared radiation are either localized in the wells or strongly mixed with barrier-bound states and therefore delocalized. The shape of the absorption line correspondingly changes from a narrow Lorentz line to a rather broad absorption band. Using the structural parameters determined by high-resolution triple-axis x-ray diffraction, the results of a self-consistent LuttingerKohn type envelope function approach with the explicit inclusion of the strain in the quantum wells are in excellent agreement with the measured spectra.