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We address the photoluminescence emission of individual germanium extrinsic centers in Al_0.3Ga0.7As epilayers grown on germanium substrates. Through a thorough analysis of micro-photoluminescence experiments we demonstrate the capability of high temperature emission (70 K) and multiexcitonic features (neutral exciton X, biexciton XX, positive X+ and negative X- charged exciton) of these quantum emitters. Finally, we investigate the renormalization of each energy level showing a large and systematic change of the binding energy of XX and X+ from positive to negative values (from ~+5 meV up to ~-7 meV covering about ~ 70 meV of the emission energy) with increasing quantum confinement. These light emitters exhibiting energy-degenerate X and XX energy levels at ~1.855 eV (680 nm) are a promising resource for the generation of entangled photons in the time-reordering scheme on a silicon platform.
We present a detailed investigation into the optical characteristics of individual InAs quantum dots (QDs) grown by metalorganic chemical vapor deposition, with low temperature emission in the telecoms window around 1300 nm. Using micro-photoluminesc
We have observed photoinduced negative optical conductivity, or gain, in the terahertz frequency range in a GaAs multiple-quantum-well structure in a strong perpendicular magnetic field at low temperatures. The gain is narrow-band: it appears as a sh
We demonstrate that the exciton and biexciton emission energies as well as exciton fine structure splitting (FSS) in single (In,Ga)As/GaAs quantum dots (QDs) can be efficiently tuned using hydrostatic pressure in situ in an optical cryostat at up to
We report on single InGaAs quantum dots embedded in a lateral electric field device. By applying a voltage we tune the neutral exciton transition into resonance with the biexciton using the quantum confined Stark effect. The results are compared to t
Optical pump-THz probe spectroscopy is used to investigate the exciton formation dynamics and its intensity dependence in bulk Ge. Associated with the intra-excitonic 1s-2p transition, the gradual build-up of an absorption peak around 3.1 meV (0.75 T