Modelling impurity: impurity interactions in silicon and experimental impurity device

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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.