We report direct evidence for the control of the oscillator strength of the exciton state in a single quantum dot by the application of a vertical electric field. This is achieved through the study of the radiative lifetime of a single InGaN-GaN quantum dot in a p-i-n diode structure. Our results are in good quantitative agreement with theoretical predictions from an atomistic tight-binding model. Furthermore, the increase of the overlap between the electron and hole wave functions due to the applied field is shown experimentally to increase the attractive Coulomb interaction leading to a change in the sign of the biexcitonic binding energy.

We report measurements of optical transitions in single III/V ͑InGaN͒ quantum dots as a function of time. Temporal fluctuations in microphotoluminescence peak position and linewidth are demonstrated and attributed to spectral diffusion processes. The origin of this temporal variation is ascribed to randomly generated local electric fields inducing a Stark shift in the optical emission peaks of the InGaN quantum dots.

The authors report on the generation of single photons in the blue spectral region from a single InGaN∕GaN quantum dot. The collection efficiency was enhanced by embedding the quantum dot layer in the middle of a low-Q microcavity. The microphotoluminescence is observed to be approximately ten times stronger than typical InGaN quantum dot emission without a cavity. The measurements were performed using nonlinear excitation spectroscopy in order to suppress the background emission from the underlying wetting layer.

Articles you may be interested inBlue single photon emission up to 200K from an InGaN quantum dot in AlGaN nanowire Appl. Phys. Lett. 102, 161114 (2013); 10.1063/1.4803441 Time-resolved and time-integrated photoluminescence studies of coupled asymmetric GaN quantum discs embedded in AlGaN barriersDiscrimination of local radiative and nonradiative recombination processes in an InGaN/GaN single-quantum-well structure by a time-resolved multimode scanning near-field optical microscopy

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Temperature dependence of the photoluminescence properties of self-assembled In Ga As ∕ Ga As single quantum dot

Time-integrated and time-resolved microphotoluminescence studies have been performed on Inx Ga1−xN quantum disks at the tips of GaN nanocolumns. The results are analyzed in the context of current theories regarding an inhomogeneous strain distribution in the disk which is theorized to generate lateral charge separation in the disks by strain induced band bending, an inhomogeneous polarization field distribution, and Fermi surface pinning. It is concluded that no lateral separation of carriers occurs in the quantum disks under investigation. Internal field screening by an increased carrier density in the QDisks at higher excitation densities is observed via a blue-shift of the emission and a dynamically changing decay time. Other possible explanations for these effects are discussed and discounted. Cathodoluminescence studies have also been carried out on the nanocolumns to provide insight into the physical origin of the luminescence.

There is a great potential in the development of versatile single‐photon devices based on nitride‐based single quantum dots due to their unique properties. Their emission can be engineered to span a wide spectral range from the ultraviolet to the blue and green regions of the spectrum which may prove important for several applications such as free‐space quantum cryptography and low‐noise absorption measurements. It is also possible to dynamically tune the wavelength of the emitted single photons over a wide range by controlling the internal piezoelectric field using externally applied electric fields. The nitrides also have the potential of providing devices which operate at relatively high temperatures. In this contribution, we review the progress made so far towards the development of optically excited and electrically driven single photon sources based on these structures.