Infrared photoluminescence and absorption of Ge/Si quantum dots with different doping levels

The influence of Ge/Si quantum dot doping level on the infrared interband photoluminescence is experimentally studied for various temperatures and pumping levels. Indirect and direct in real space optical transitions are identified in the luminescence spectra. Effect of doping on equilibrium and photoinduced absorption spectra is also experimentally studied in mid- and far-infrared (terahertz) spectral ranges for different temperatures. The features in the absorption spectra are explained with the contribution of the optical hole transitions from the ground state to the excited states of quantum dots and to the extended states of the continuous spectrum.