Voltage–capacitance and admittance investigations of electron states in self-organized InAs/GaAs quantum dots

Emission of electrons from localized electron states in InAs/GaAs self-organized quantum dots (QDs) grown by MOCVD has been studied by a combination of steady-state voltage–capacitance and admittance techniques. We have found a fine structure of carrier concentration profile in the area of QDs, which may be attributed to ground and excited energy states of electrons in the QDs. The total range of activation energies detected in the admittance investigations extends from 20 meV up to 140 meV and testifies to the significant inhomogeneous broadening of the density of state function due to the QD scattering in geometric sizes.