Plasmonic enhancement of four-particle radiative recombination in SiGe quantum wells

The influence of gold nanoparticles deposited on the surface of a Si_0.95Ge_0.05/Si quantum-well heterostructure with a thin Si cap layer on the spectra of low-temperature recombination radiation of biexcitons and an electron–hole liquid confined in the quantum well is investigated. The spectra of both visible and near-infrared radiation are recorded from a region on the sample surface without nanoparticles and regions coated with nanoparticles of different areal densities. It is found that the presence of gold nanoparticles causes strong plasmonic enhancement of collective emission processes in which two holes simultaneously recombine with two electrons from opposite valleys of the conduction band, with the energy of the four particles being transferred to a single photon in the visible spectral range.