Intraband absorption and photocurrent spectroscopy of self-assembled p-type Si/SiGe quantum dots

In infrared transmission and photocurrent spectra of self-assembled SiGe quantum dot samples grown in the Stranski-Krastanow mode at temperatures around T=520°C different types of transitions are observed: in the transmission experiments, an absorption line due to bound-to-bound transitions is measured whereas the photocurrent spectra are determined by bound-to-continuum transitions. The experimental determination of the energies of both types of transitions for the same sample allows a detailed discussion of the features observed in the spectra as well as an estimate of the average Ge content in the dots.