Doping dependence of intersubband transitions in Si1−xGexSi multiple quantum wells

Effect of doping on the intersubband transition of p-type SiGeSi multiple quantum wells has been studied. Three Si0.6Ge0.4Si multiple quantum well structures (10 periods each) with doping concentrations from 1 × 1019 cm−3 to 4 × 1020 cm−3 grown by Si molecular beam epitaxy were used in the experiment. It was found that as the doping in the quantum well is increased the peak position of the transition moves to a higher energy. This behavior is due to the formation of δ-like potential well inside the quantum well and the collective nature of the intersubband transitions. In orther to assess the experimental data, transition energies for different doping concentrations are calculated using a self-consistent scheme. The experimental data are in good agreement with the calculation if the many-body effects are incorporated. This work demonstrates the importance of doping effects in the design of quantum well IR detectors.