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^{1,2}, E. Prati

^{2}, M. Belli

^{2}, G. Leti

^{2}, S. Cocco

^{2}, M. Fanciulli

^{1,2}, F. Guagliardo

^{3}and G. Ferrari

^{3}

### Abstract

We report on the charge transfer dynamics between a siliconquantum dot and an individual phosphorous donor extracted from the current through the quantum dot as a probe for the donor ionization state. We employ a silicon*n*-metal-oxide-semiconductor field-effect transistor (MOSFET) with two side gates at a single metallization level to control both the device conductance and the donor charge. The elastic nature of the process is demonstrated by temperature and magnetic field independent tunneling times. The Fano factor approaches 1/2 revealing that the process is sub-poissonian.

This work was partly supported by the CARIPLO Foundation national project ELIOS.

##### H01L29/00

## Figures

(a) Schematic depiction of the device under investigation and representation of the circuit connections. (b) Drain-source current vs. main gate bias measured near threshold at 4.2 K. The applied drain-source bias was 1 mV and the side gate bias was 0 V.

(a) Schematic depiction of the device under investigation and representation of the circuit connections. (b) Drain-source current vs. main gate bias measured near threshold at 4.2 K. The applied drain-source bias was 1 mV and the side gate bias was 0 V.

Derivative of the drain-source current vs. side gate bias () as a function of main gate and side gates polarization at 4.2 K. The diagram represents the merging of three distinct measurements which probe different regions in the plane. The arrows indicate the discontinuity lines attributed to donor ionizations. The bold arrow indicates the working point adopted for charge dynamics investigations.

Derivative of the drain-source current vs. side gate bias () as a function of main gate and side gates polarization at 4.2 K. The diagram represents the merging of three distinct measurements which probe different regions in the plane. The arrows indicate the discontinuity lines attributed to donor ionizations. The bold arrow indicates the working point adopted for charge dynamics investigations.

Detail of vs. and diagram at 4.2 K near the ionization of a single donor. The solid and dashed lines represent the borders of charge stability regions for the quantum dot and the donor, respectively. Current flow is only observed along the quantum dot charge stability line. The numbers in brackets represent the quantum dot and the donor occupation, respectively, in each charge stability region.

Detail of vs. and diagram at 4.2 K near the ionization of a single donor. The solid and dashed lines represent the borders of charge stability regions for the quantum dot and the donor, respectively. Current flow is only observed along the quantum dot charge stability line. The numbers in brackets represent the quantum dot and the donor occupation, respectively, in each charge stability region.

(a) Detail of the scan of the drain-source current as a function of and at 300 mK. The circles mark the two bias points used for measuring the average tunneling times, while the solid arrow represents the line along which the potential is moved during the RTS experiments. (b) Average of the transient quantum dot current acquired after the sudden switching of the bias point to allow tunneling of one electron into the donor state (example of capture time measurement). (c) and (d) Dependence of the average tunneling time as a function of the temperature (c) and the magnetic field (d) applied in-plane.

(a) Detail of the scan of the drain-source current as a function of and at 300 mK. The circles mark the two bias points used for measuring the average tunneling times, while the solid arrow represents the line along which the potential is moved during the RTS experiments. (b) Average of the transient quantum dot current acquired after the sudden switching of the bias point to allow tunneling of one electron into the donor state (example of capture time measurement). (c) and (d) Dependence of the average tunneling time as a function of the temperature (c) and the magnetic field (d) applied in-plane.

(a) Typical RTS trace acquired near the ionization point of the donor. The signal is reconstructed via a threshold algorithm before performing statistical analyses. (b) Average values for the tunneling rates and as a function of the detuning energy and fitting according to Eq. (1). The arrows mark the fluctuations in that can be attributed to resonant tunneling to the orbitals in the quantum dot. (c) and (d) Average number of tunneling events per unit time (c) and Fano factor (d) extracted from the RTS traces. In both diagrams, the solid lines represent the theoretical trend extracted from the FCS model using the parameters obtained from the fit of the data in (b).

(a) Typical RTS trace acquired near the ionization point of the donor. The signal is reconstructed via a threshold algorithm before performing statistical analyses. (b) Average values for the tunneling rates and as a function of the detuning energy and fitting according to Eq. (1). The arrows mark the fluctuations in that can be attributed to resonant tunneling to the orbitals in the quantum dot. (c) and (d) Average number of tunneling events per unit time (c) and Fano factor (d) extracted from the RTS traces. In both diagrams, the solid lines represent the theoretical trend extracted from the FCS model using the parameters obtained from the fit of the data in (b).

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