Modelling impurity: impurity interactions in silicon and experimental impurity device

Lead Research Organisation: University of Surrey
Department Name: ATI Physics


Impurities in silicon provide a promising platform for quantum computing due to the long coherence lifetimes of the available quantum states of the impurities. Silicon has a long pedigree as a material for microelectronic engineering. It can be refined to a high chemical purity and microfabrication techniques used on it in modern classical electronics are well established. To make use of the quantum nature of single dopants as qubits individual dopants must be able to interact with other dopants to perform gate operations and yet be able to be isolated such that they may retain their quantum information over the time of the operation. To introduce substitutional impurities in the silicon lattice, broad area ion implantation is a convenient method. However, this technique places the impurities stochastically in the substrate with limited control over the resulting distance between impurities.

The quantum mechanical interactions between impurities in this system are sensitive to nearest neighbour distances therefore dopants introduced via ion implantation will have neighbour distances described by the underlying point processes. This project will begin by exploring the nearest neighbour statistics describing ion-implanted semiconductors looking to optimise implant conditions for useful clusters whereby the optical excitation of one species of impurity gates an interaction between impurities of another species. Spectroscopic techniques using THz radiation will be used on large area ion implanted silicon devices to characterise the interactions occurring between the impurities themselves, and between the impurities and the metal contacts used to measure photocurrent across the device. This concept will be scaled down to fabricate and study device whose photo-electronic properties depends on the electronic quantum state of a single implanted impurity. Such a device would demonstrate a method of quantum state readout of a qubit in silicon.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509772/1 01/10/2016 30/09/2021
1911314 Studentship EP/N509772/1 03/07/2017 03/07/2020 Kristian Stockbridge
Description A statistical method was developed for optimising the nearest neighbour configuration of ion implanted donors in silicon. The optimised multispecies cluster of relevance is a proposed scheme of qubit gate in solid state quantum technology. Prior to this study it was not known whether introducing donor qubits via ion implantation gave a statistical advantage in this regard over bulk doping or the 2D equivalent. Nor was the method by which to calculate such probabilities clearly published.
Exploitation Route The proposed optimum doping parameters as published may be used to more easily and more cheaply fabricate testbed samples in which the spin entanglement of frozen-out donor electrons via the orbital excitation of intermediary donors may be observed. This would demonstrate experimentally the ability to perform gated entanglement operations in an ion implanted solid state quantum computing platform.
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Other

Description Outreach (Cheltenham science festival) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact I spoke to members of the general public along with many school groups from a stall in the event's 'Discover Zone' area. Here I spoke about my research in the field of donors in silicon for quantum technology with the intention of raising awareness of why a quantum computer is a useful tool and how one might fabricate its component parts from silicon.
Year(s) Of Engagement Activity 2019