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^{1,a)}, K. R. Brown

^{1,b)}and B. E. Kane

^{1}

### Abstract

We incorporate an single-electron transistor as the gate of a narrow metal-oxide-semiconductorfield-effect transistor(MOSFET). Near the MOSFET channel conductance threshold, we observe oscillations in the conductance associated with Coulomb blockade in the channel, revealing the formation of a Si single-electron transistor. Abrupt steps present in sweeps of the Al transistor conductance versus gate voltage are correlated with single-electron charging events in the Si transistor, and vice versa. Analysis of these correlations using a simple electrostatic model demonstrates that the two single-electron transistor islands are closely aligned, with an interisland capacitance approximately equal to of the total capacitance of the Si transistor island, indicating that the Si transistor is strongly coupled to the Al transistor.

This work was supported by the Laboratory for Physical Sciences.

### Key Topics

- MOSFETs
- 12.0
- Single electron transistors
- 10.0
- Capacitance
- 6.0
- Coulomb blockade
- 5.0
- Electrostatics
- 4.0

## Figures

(Color) (a) SEM image of a typical device. The Al SET island forms during the second of two evaporations at different angles. (b) Schematic of the measurement circuit. The conductance of each SET is measured using independent circuits. The red region represents the MOSFET conducting channel confined between the two regions. The circles containing the letter “A” represent current-sensitive amplifiers. (c) Coulomb blockade oscillations of the Si SET differential conductance as a function of the relative bias between the Al SET and the Si SET at .

(Color) (a) SEM image of a typical device. The Al SET island forms during the second of two evaporations at different angles. (b) Schematic of the measurement circuit. The conductance of each SET is measured using independent circuits. The red region represents the MOSFET conducting channel confined between the two regions. The circles containing the letter “A” represent current-sensitive amplifiers. (c) Coulomb blockade oscillations of the Si SET differential conductance as a function of the relative bias between the Al SET and the Si SET at .

(Color) Simultaneously measured conductances of both SETs. [(a) and (c)] Coulomb blockade oscillations of the Al and Si SET conductances, respectively, at . [(b) and (d)] Conductance of the Al and the Si SET, respectively, vs and .

(Color) Simultaneously measured conductances of both SETs. [(a) and (c)] Coulomb blockade oscillations of the Al and Si SET conductances, respectively, at . [(b) and (d)] Conductance of the Al and the Si SET, respectively, vs and .

(Color) Conductance maxima of both SETs vs and . Red dots and blue dots are Gaussian fits to the data in Figs. 2(b) and 2(d), respectively. Black lines are a linear fit to the points on each edge. The regions labeled a, b, c, and d are the four hexagons whose parameters are presented in Table I.

(Color) Conductance maxima of both SETs vs and . Red dots and blue dots are Gaussian fits to the data in Figs. 2(b) and 2(d), respectively. Black lines are a linear fit to the points on each edge. The regions labeled a, b, c, and d are the four hexagons whose parameters are presented in Table I.

(Color) (a) Circuit model for the coupled SET system. and are the number of electrons on the Al and the Si SET island, respectively. Due to the very small drain-source bias of each SET, we can simplify the two tunnel barrier capacitances for each SET to a single capacitance ( and ) as shown. (b) Hexagonal phase diagram based on the model in (a). Each hexagon represents a configuration with a different number of charges on the SET islands. , , and are the slopes of the hexagon edges. , , and are the separations between opposite parallel edges of the hexagon.

(Color) (a) Circuit model for the coupled SET system. and are the number of electrons on the Al and the Si SET island, respectively. Due to the very small drain-source bias of each SET, we can simplify the two tunnel barrier capacitances for each SET to a single capacitance ( and ) as shown. (b) Hexagonal phase diagram based on the model in (a). Each hexagon represents a configuration with a different number of charges on the SET islands. , , and are the slopes of the hexagon edges. , , and are the separations between opposite parallel edges of the hexagon.

## Tables

Capacitances of the four hexagons labeled in Fig. 3 for the circuit model in Fig. 4.

Capacitances of the four hexagons labeled in Fig. 3 for the circuit model in Fig. 4.

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