Electron- and hole-related electrical activity of InAs/GaAs quantum dots

The electron- and hole-related electrical activity of the InAs/GaAs quantum dot system has been demonstrated with a use of the high-resolution Laplace and conventional DLTS methods combined with below GaAs bandgap illumination. Without the illumination, the DLTS signal refers to the emission process of electrons bound by the dot confining potential in the conduction band. In this experimental mode, single- and double-electron states of the dot could be observed. The resolution of the method allows both charge states of the dot to be observed in the same Laplace DLTS spectrum and thus the relative occupancy factor for both charge states can be determined. This gives the value of the Coulomb blockade energy (∼11 meV). When prior to the DLTS signal detection a short below-bandgap illumination resonant with the dot excitonic energy is applied, a non-equilibrium hole occupancy in the dot is created. This allows the same dots to be studied in order to establish the hole-referred electrical dot activity governed by the confining potential in the valence band. © 2007 Elsevier B.V. All rights reserved.