## Coulomb Blockade

Understanding and modeling of physics on an atomic scale is crucial for the continued miniaturization and development of novel semiconductor devices. In this project, we investigate electron transport in quantum dots. Semiconductor quantum dots are nanometer-sized structures that confine charge carriers in all three spatial dimensions. In particular, quantum dots are seen as promising candidates for the realization of qubits or single electron transistors (SET). Recent advances in solid-state nanoelectronics have enabled an Australian group of experimentalists (Dr. Simmons) the controlled fabrication of electrostatically gated quantum dots defined by single phosphor impurities (world’s smallest transistor to date). In collaboration with Dr. Simmons, this project aims to provide further physical insight into the fabricated quantum dot device through our group’s expertise in computational nanotechnology. In particular, the objectives of our work are to:

- Model experimentally measured charge stability diagrams (Coulomb diamonds)
- Investigate electron transport in the Coulomb-blockaded transport regime based on a rate-equation approach
- Analyze experimental effects such as atomistic disorder and channel-lead interfaces
- Substantiate the existence and functionality of the world’s smallest transistor from a theoretical modeling perspective

### Group Members Involved:

### References

- M. Fuechsle, S. Mahapatra, F.A. Zwanenburg, M. Friesen, Nature Nanotechnology, 5, 502 (2010)
- G. Klimeck, R. Lake, S. Datta, Physical Review B, Vol. 50, Nr. 8, 1994
- C.W.J. Beenakker, Physical Review B, Vol. 44, Nr. 4, 1991

STM image of a few-electron single crystal silicon quantum dot (Reference 1)

Illustration of rate-equation formalism for sample quantum dot

(Dissertation G. Klimeck, Electron-Phonon and Electron-Electron Interactions in Quantum Transport

Simulated charge stability diagrams (Coulomb diamonds) of a) quantum dot with 5-spin degenerate states b) quantum dot with varying lead density of states (DOS)