We have performed transport experiments on two-dimensional electron gases in a GaAsAl0.3Ga0.7As heterostructure containing InAs self-assembled quantum dots in close proximity to the heterointerface. We find that the dots act as repulsive scatterers and dominate the mobility. In the samples with the highest dot density, we find a metal-insulator transition, which differs from such transitions in other samples in several respects.

We used capacitance, photocurrent and photoluminescence spectroscopy to investigate the dynamics of optically excited electron-hole pairs in InAs self assembled quantum dots under different electric field and charging conditions. Since a change in the laser wavelength does not affect the position of the characteristic features in the photocurrent signal, we assume that the optically excited carriers relax into the quantum dot ground state before recombination processes or tunneling out of the quantum dot occur. The field range can be separated into a high field regime, where the carriers tunnel out of the quantum dot, and a low-field regime, where the exciton is trapped in the dot and recombines. When the quantum dots are loaded with electrons from the back contact, the ground state transition in the photoluminescence spectra shifts from E approximate to 1.052eV down to E approximate to 1.039eV and the full width at half maximum increases from 33meV to 38meV accompanied by a decrease in intensity by a factor of 2. In addition to the QD ground state a higher excited state transition appears at E approximate to 1.11eV which is explained by a recombination process between an electron in the quantum dot d-shell and a hole in the s-shell. All the bias induced effects described above can be explained in terms of manybody interaction in charged QDs and are in excellent agreement with theory.