Interband absorption on self-assembled InAs quantum dots

We have studied the interband excitations of an ensemble of InAs self-assembled quantum dots by detecting absorption directly in transmission experiments. The dots are embedded in a MISFET structure, allowing the dots' electron occupation to be controlled with a gate voltage. We show how Coulomb blockade in the device's C - V-g characteristic corresponds to Pauli blocking of optical transitions in transmission. Furthermore, the second absorption peak of the dots shifts by some 20 meV and weakens when the first electron level is filled with two electrons, evidence of an exciton-electron interaction. The results also provide a direct measurement of the oscillator strength of the dots. (C) 1998 Elsevier Science B.V. All rights reserved.