Probing the band structure of InAs/GaAs quantum dots by capacitance-voltage and photoluminescence spectroscopy

The band structure of self-assembled InAs quantum dots, embedded in a GaAs matrix, is probed with capacitance-voltage spectroscopy and photoluminescence(PL)spectroscopy. The electron energy levels in the quantum dots with respect to the electron ground state of the wetting layer (WL) are determined from the capacitance-voltage measurements with a linear lever arm approximation. In the region where the linear lever arm approximation is not valid anymore (after the charging of the WL), the energetic distance from the electron ground state of the WL to the GaAs conduction band edge can be indirectly inferred from a numerical simulation of the conduction band under different gate voltages. In combination with PL measurements, the complete energy band diagram of the quantum dot sample is extracted

Experimental imaging and atomistic modeling of electron and hole quasiparticle wave functions in InAs/GaAs quantum dots

We present experimental magnetotunneling results and atomistic pseudopotential calculations of quasiparticle electron and hole wave functions of self-assembled InAs/GaAs quantum dots. The combination of a predictive theory along with the experimental results allows us to gain direct insight into the quantum states. We monitor the effects of (i) correlations, (ii) atomistic symmetry and (iii) piezoelectricity on the confined carriers and (iv) observe a peculiar charging sequence of holes that violates the Aufbau principle.Comment: Submitted to Physical Review B. A version of this paper with figures can be found at http://www.sst.nrel.gov/nano_pub/mts_preprint.pd

Coulomb-interaction induced incomplete shell filling in the hole system of InAs quantum dots

We have studied the hole charging spectra of self-assembled InAs quantum dots in perpendicular magnetic fields by capacitance-voltage spectroscopy. From the magnetic field dependence of the individual peaks we conclude that the s-like ground state is completely filled with two holes but that the fourfold degenerate p-shell is only half filled with two holes before the filling of the d-shell starts. The resulting six-hole ground state is highly polarized. This incomplete shell filling can be explained by the large influence of the Coulomb interaction in this system.Comment: Accepted for publication in Physical Review Letter

Mapping of the hole wave functions of self-assembled InAs-quantum dots by magneto-capacitance-voltage spectroscopy

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Magnetic-field-induced modification of the wave-functions in InAs quantum dots

The probability density of electrons in self-assembled InAs quantum dots is investigated by tunneling magnetocapacitance-voltage spectroscopy. A magnetic field in the plane of the tunneling layer is used to shift the momentum of the electrons tunneling into the dots and this way map the wave functions in k-space. When an additional perpendicular magnetic field is applied, a clear modification of the shape of the "p-state" wave functions is observed. In particular, the p+-state changes from x, y-symmetry with a node along one crystal orientation to an almost circularly symmetric shape when the perpendicular magnetic field is increased from 0 to 9 T