Relaxation-induced lattice misfits and their effects on the emission properties of InAsquantum dots

Abstract

Strain relaxation in InAs/InGaAs quantum dots (QDs) is shown to introduce misfits in theQD and neighboring GaAs bottom layer. A capacitance–voltage profiling shows an electronaccumulation peak at the QD with a long emission time, followed by additional carrierdepletion caused by the misfits in the GaAs bottom layer. The emission-time increase isexplained by the suppression of tunneling for the QD excited states due to the additionalcarrier depletion. As a result, electrons are thermally activated from the QD states to theGaAs conduction band, consistent with observed emission energies of 0.160 and0.068 eV which are comparable to the confinement energies of the QD electronground and first-excited states, respectively, relative to the GaAs conduction band.This is in contrast to non-relaxed samples in which emission energy of 60 meV isobserved, corresponding to the emission from the QD ground state to the first-excitedstate.