Effect of Charge Distribution in Quantum Dots Array on Two-Dimensional Electron Gas

With InGaAs quantum dots (QDs) embedded in the vicinity, GaAs/AlGaAs two-dimensional electron gas (2DEG) was studied by transport measurements and by calculations with QDs charges as Coulomb scattering centers. The mobility of 2DEG decreases with increasing QDs density up to 5×1010 cm-2, which can be fitted by considering the finite spatial extension of QD-charge distribution. However, two distinct effects are observed as the QDs density increases from 5×1010 cm-2 to 2×1011 cm-2. One is that the 2DEG mobility is saturated at a low level, and the other is that it gradually approaches the high value of 2DEG without QDs. The former can be reproduced by taking into account the interdot overlapping of electron probability distributions, while the latter is argued to be the result of interdot coupling through wavefunction overlapping. These explanations are supported further by the temperature dependence of the conductance.