Direct Quantitative Electrical Measurement of Many-Body Interactions in Exciton Complexes in InAs Quantum Dots

Abstract

We present capacitance-voltage spectra for the conduction band states of InAs quantum dots obtained under continuous illumination. The illumination leads to the appearance of additional charging peaks that we attribute to the charging of electrons into quantum dots containing a variable number of illumination-induced holes. By this we demonstrate an electrical measurement of excitonic states in quantum dots. Magnetocapacitance-voltage spectroscopy reveals that the electron always tunnels into the lowest electronic state. This allows us to directly extract, from the highly correlated many-body states, the correlation energy. The results are compared quantitatively to state of the art atomistic configuration interaction calculations, showing very good agreement for a lower level of excitations and also limitations of the approach for an increasing number of particles. Our experiments offer a rare benchmark to many-body theoretical calculations.

Thermal shift of the resonance between an electron gas and quantum dots: what is the origin?

“…Such an excitonic peak appears at low temperatures, when the Fermi energy is aligned to the electron eigenenergy in the QD charged by a number of holes via illumination [11]. These eigenenergy originate from attractive Coulomb interaction of the holes and the electron and thus appear at lower gate voltages than the s-charging peaks.…”

“…QD h An analysis of the gate voltage dependency yields a smooth bias dependency of the rate (see figure 3, supplemental material). Labud et al [11] show, that the excitonic peak-position is barely hole generation rate dependent by varying the illumination intensity nearly two orders of magnitude, while the smooth bias depence would imply such a dependency. Thus this spatial indirect recombination has to be less important and another effect with a steep increase in rate must be responsible for the observed excitonic peak and its temperature shift.…”

“…Warburton et al modelled the different types of Coulomb-interaction in such systems and derived the corresponding energies theoretically [9]. Recently, it has been shown, that by creating holes in self-assembled QDs in a Schottky-diode under illumination, also excitons of different charge-state can be detected electrically [10,11]. Bayer and Forchel [12] performed temperature dependent investigations and determined the QD's homogenous linewidth increasing only by a tiny amount compared to k B T, making QDs promising candidates for higher temperature applications.…”

Electron dynamics in transport and optical measurements of self‐assembled quantum dots

“…They exhibit a strong confinement for higher operation temperatures above K and can be addressed by both, optical (due to their large optical dipol moment) and electrical methods. These self‐assembled QDs, , like an atom, show energy quantization, direct and indirect (exchange) Coulomb interaction as well as angular momentum and spin‐dependent optical, , and electrical properties, . Moreover, recent discoveries of nuclear spin manipulation, and decoupling from these nuclear spins () make self‐assembled dots highly attractive for quantum applications where long spin coherence is needed.…”

“…In capacitance–voltage, or transport spectroscopy, , the electron or hole states are measured independently with their Coulomb and exchange interaction. The electron–hole interaction is absent in such electrical measurements (for an exception, see Labud et al ()), where the QD has to be coupled to a charge reservoir. This reservoir provides the charge carriers, and can be used for electrical contacting and for the read‐out in transconductance spectroscopy.…”