Influence of quasi-two-dimensional doping on the Raman spectrum of Si1−xGex/Si quantum wells

We present a study of p-doping influence on the Raman spectrum of thin SiGe quantum wells. We observe a laser wavelength dependence of the phonon frequencies. We show that the quantum confinement induces special effects which can be described by the renormalization of the phonon energy by the free charge continuum transitions. It is shown that the polarization of the laser and of the phonon can probe the confinement and the density of states of the quasi-free holes.