Intersubband absorption in Si1−xGex/Si multiple quantum wells

Abstract

The intersubband infrared absorption of holes in Si_1−xGe_x/Si multiple quantum wells is observed. The quantum well structure consists of 10 periods of 40−Å−thick Si_0.6Ge_0.4 wells and 300−Å−thick Si barriers. The samples are prepared using molecular beam epitaxy. In the experiment, the infrared absorption as a function of wavelength is measured using a waveguide geometry. An absorption peak near 8.1 μm has been observed, which is due to the transition between first two heavy hole bound states. The polarization dependence spectra are in good agreement with the selection rules for the intersubband transition.