Intersubband transitions of boron-doped self-assembled Ge quantum dots

Infrared intersubband absorption and photocurrent investigations of self-assembled Ge quantum dots grown by molecular beam epitaxy in the Stranski–Krastanow mode at temperatures around T=520°C are reported. In transmission experiments, absorption due to bound-to-bound transitions have been observed whereas the photocurrent spectra are determined by bound-to-continuum transitions. Since both types of experiments were performed on the same sample, the transmission and photocurrent spectra can directly be compared and allow a detailed discussion of the energy levels for one and the same set of quantum dots.