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Excited states of defect linear arrays in silicon: A first-principles study based on hydrogen cluster analogues

Wu, W, Greenland, P, Fisher, A, Le, Huy Nguyen, Chick, Steven and Murdin, Benedict (2018) Excited states of defect linear arrays in silicon: A first-principles study based on hydrogen cluster analogues Physical Review B, 97 (3), 035205.

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Excited states of a single donor in bulk silicon have previously been studied extensively based on effective mass theory. However, proper theoretical descriptions of the excited states of a donor cluster are still scarce. Here we study the excitations of lines of defects within a single-valley spherical band approximation, thus mapping the problem to a scaled hydrogen atom array. A series of detailed full configuration-interaction, time-dependent Hartree-Fock and time-dependent hybrid density-functional theory calculations have been performed to understand linear clusters of up to 10 donors. Our studies illustrate the generic features of their excited states, addressing the competition between formation of inter-donor ionic states and intra-donor atomic excited states. At short interdonor distances, excited states of donor molecules are dominant, at intermediate distances ionic states play an important role, and at long distances the intra-donor excitations are predominant as expected. The calculations presented here emphasise the importance of correlations between donor electrons, and are thus complementary to other recent approaches that include effective mass anisotropy and multi-valley effects. The exchange splittings between relevant excited states have also been estimated for a donor pair and for three-donor arrays; the splittings are much larger than those in the ground state in the range of donor separations between 10 and 20 nm. This establishes a solid theoretical basis for the use of excited-state exchange interactions for controllable quantum gate operations in silicon.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Electronic Engineering
Authors :
Wu, W
Greenland, P
Fisher, A
Le, Huy
Date : 29 January 2018
Funders : UKRC
DOI : 10.1103/PhysRevB.97.035205
Copyright Disclaimer : Copyright 2018 American Physical Society
Depositing User : Melanie Hughes
Date Deposited : 06 Mar 2018 10:39
Last Modified : 11 Dec 2018 11:23

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