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Fabrication and characterization of nanoscale dopant devices in silicon

Koelker, Alexander; (2018) Fabrication and characterization of nanoscale dopant devices in silicon. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Semiconductor nanostructures consisting of areas of buried dopant atom(s) are crucial com- ponents for present and future complementary metal-oxide-semiconductor (CMOS) transistor technologies as well as for emerging quantum computing architectures. This thesis describes electrically contacted nanoscale devices of buried phosphorus in silicon, fabricated using scanning tunnelling microscope (STM) based hydrogen resist lithography, and char- acterised using scanning microwave microscopy (SMM). The goal is to improve nanoscale device fabrication strategies and develop methods that allow a direct device characterisation for a broad range of applications such as the fabrication of a silicon quantum computer. At first, a step by step guide for the fabrication strategy that has been developed is presented. The resulting nanoscale devices, consisting of a single layer of phosphorus atoms in silicon (so called δ-layers), are characterised by electrical transport measurements and SMM. The transport measurements enable the study of the sensitivity of conduction to small changes in dopant densities and the determination of the δ-layer ’electronic width’, along with the growth quality of the δ -layers. The second part of the thesis describes the development of a characterisation scheme using SMM that not only enables us to non-destructively image atomically-thin patterned nanostructures buried in silicon, but also extract quantitative parameters such as depth and conductance. This scheme was subsequently applied to extract similar parameters from a three-dimensional (3D) sample, whose complexity and difficulty of fabrication far exceeds any other published 3D P-in-Si structure made using hydrogen resist lithography. We also demonstrate that SMM spectroscopy in conjunction with finite element modelling can be employed to identify the contributions to the measured SMM complex admittance that orig- inate from the substrate, the patterned δ-layer region and the two-dimensional (2D) nature of the two-dimensional electron gas (2DEG). Finally, characterisation is performed on an active P-in-Si patterned device component in the form of a 1μm×10μm wire with an in-plane bias applied along the wire. The full range of scanning probe capabilities of an SMM setup is applied for characterisation, including Kelvin probe force microscope (KPFM) and scanning capacitance force microscope (SCFM).

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Fabrication and characterization of nanoscale dopant devices in silicon
Event: University College London
Language: English
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: http://discovery.ucl.ac.uk/id/eprint/10055996
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