Fermi-edge singularity in p-type modulation-doped SiGe quantum wells

A strong effect of p-type modulation doping on the radiative recombination in Si/Si1-xGex/Si quantum wells is observed by photoluminescence (PL) spectroscopy. The filling of the Si-Ge quantum wells due to the charge transfer of holes from the B modulation doping in the adjacent Si layers causes an appearance of a broad asymmetric PL band with a characteristic sharp high-energy cutoff. A strong enhancement near the Fermi edge is shown, by varying structure parameters and experimental conditions, to correspond to the Fermi-edge singularity. Experimental evidence on the dominant mechanism responsible for the Fermi-edge singularity is given as due to a nearly resonant scattering between the electronic states near the Fermi energy and the next unoccupied subband of the two-dimensional hole gas.