Blueshifts in the photoluminescence emission energies from an ensemble of self-assembled InAs quantum dots are observed as a result of postgrowth thermal annealing. Enhancement of the integrated photoluminescence emission and narrowing of the full width half-maxima (from 55 to 12 meV) occur together with blueshifts up to 300 meV at annealing temperatures up to 950 °C. Evidence that the structures remain as dots comes form the observation of level filling and photoluminescence excitation studies which reveal LO phonon peaks occurring at multiples of ∼30 meV from the detection energies.

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We have observed a Fermi-edge singularity in the tunneling current between a two-dimensional electron gas (2DEG) and a zero-dimensional localized state. A sharp peak in the tunnel current is observed when the energy of the localized state matches the Fermi energy of the 2DEG. The peak gro~s and becomes sharper as the temperature is decreased to our lowest temperature of 70 mK. We attribute the singularity to the Coulomb interaction between the tunneling electron on the localized site and the Fermi sea.

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