{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T04:29:04Z","timestamp":1772252944234,"version":"3.50.1"},"reference-count":16,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2018,9,22]],"date-time":"2018-09-22T00:00:00Z","timestamp":1537574400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000266","name":"Engineering and Physical Sciences Research Council","doi-asserted-by":"publisher","award":["EP\/N00275X\/1"],"award-info":[{"award-number":["EP\/N00275X\/1"]}],"id":[{"id":"10.13039\/501100000266","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000266","name":"Engineering and Physical Sciences Research Council","doi-asserted-by":"publisher","award":["EP\/N00275X\/1"],"award-info":[{"award-number":["EP\/N00275X\/1"]}],"id":[{"id":"10.13039\/501100000266","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Europium is the most-studied and least-well-understood rare earth ion (REI) dopant in GaN. While attempting to increase the efficiency of red GaN light-emitting diodes (LEDs) by implanting Eu+ into p-type GaN templates, the Strathclyde University group, in collaboration with IST Lisbon and Unipress Warsaw, discovered hysteretic photochromic switching (HPS) in the photoluminescence spectrum of doubly doped GaN(Mg):Eu. Our recent work, summarised in this contribution, has used time-, temperature- and light-induced changes in the Eu intra-4f shell emission spectrum to deduce the microscopic nature of the Mg-Eu defects that form in this material. As well as shedding light on the Mg acceptor in GaN, we propose a possible role for these emission centres in quantum information and computing.<\/jats:p>","DOI":"10.3390\/ma11101800","type":"journal-article","created":{"date-parts":[[2018,9,24]],"date-time":"2018-09-24T10:38:49Z","timestamp":1537785529000},"page":"1800","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Hysteretic Photochromic Switching (HPS) in Doubly Doped GaN(Mg):Eu\u2014A Summary of Recent Results"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7671-7698","authenticated-orcid":false,"given":"Paul R.","family":"Edwards","sequence":"first","affiliation":[{"name":"SUPA Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG, UK"}]},{"given":"Kevin P.","family":"O\u2019Donnell","sequence":"additional","affiliation":[{"name":"SUPA Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG, UK"}]},{"given":"Akhilesh K.","family":"Singh","sequence":"additional","affiliation":[{"name":"SUPA Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG, UK"},{"name":"Alternative Energy Materials, CSIR-National Physical Laboratory, New Delhi-110012, India"}]},{"given":"Douglas","family":"Cameron","sequence":"additional","affiliation":[{"name":"SUPA Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG, UK"}]},{"given":"Katharina","family":"Lorenz","sequence":"additional","affiliation":[{"name":"INESC\/MN, IPFN, Instituto Superior T\u00e9cnico, Universidade de Lisboa, Campus Tecnol\u00f3gico e Nuclear, Estrada Nacional 10, 2695-066 Bobadela LRS, Portugal"}]},{"given":"Mitsuo","family":"Yamaga","sequence":"additional","affiliation":[{"name":"Department of Mathematical and Design Engineering, Gifu University, Gifu 501-1193, Japan"}]},{"given":"Jacob H.","family":"Leach","sequence":"additional","affiliation":[{"name":"Kyma Technologies, 8829 Midway West Rd, Raleigh, NC 27612, USA"}]},{"given":"Menno J.","family":"Kappers","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK"}]},{"given":"Michal","family":"Bo\u0107kowski","sequence":"additional","affiliation":[{"name":"Institute of High Pressure Physics PAS, Sokolowska 29\/37, 01-142 Warsaw, Poland"}]}],"member":"1968","published-online":{"date-parts":[[2018,9,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"O\u2019Donnell, K.P., and Dierolf, V. (2010). Rare-Earth Doped III-Nitrides for Optoelectronic and Spintronic Applications. Topics in Applied Physics 124, Springer.","DOI":"10.1007\/978-90-481-2877-8"},{"key":"ref_2","unstructured":"O\u2019Donnell, K.P. (2012). 2012 UKNC Winter Meeting, University of Bath. Unpublished talk."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"41982","DOI":"10.1038\/srep41982","article-title":"Hysteretic photochromic switching of Eu-Mg defects in GaN links the shallow transient and deep ground states of the Mg acceptor","volume":"7","author":"Singh","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"142114","DOI":"10.1063\/1.3383236","article-title":"Dual nature of acceptors in GaN and ZnO: The curious case of the shallow MgGa deep state","volume":"96","author":"Lany","year":"2010","journal-title":"Appl. Phys. Lett."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"156403","DOI":"10.1103\/PhysRevLett.108.156403","article-title":"Shallow versus deep nature of Mg acceptors in nitride semiconductors","volume":"108","author":"Lyons","year":"2012","journal-title":"Phys. Rev. Lett."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"241105","DOI":"10.1063\/1.5001143","article-title":"Luminescence of Eu3+ in GaN(Mg, Eu): Transitions from the 5D1 level","volume":"111","author":"Singh","year":"2017","journal-title":"Appl. Phys. Lett."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"65106","DOI":"10.1088\/1361-6463\/aaa1cc","article-title":"Eu-Mg defects and donor-acceptor pairs in GaN: Photodissociation and the excitation transfer problem","volume":"51","author":"Singh","year":"2018","journal-title":"J. Phys. D."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1051\/epjap:2006122","article-title":"Rare earth doped III-nitrides for optoelectronics","volume":"36","author":"Hourahine","year":"2006","journal-title":"Eur. Phys. J. Appl. Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"022102","DOI":"10.1063\/1.4939631","article-title":"Crystalfield symmetries of luminescent Eu3+ centers in GaN: The importance of the 5D0 to 7F1 transition","volume":"108","author":"Edwards","year":"2016","journal-title":"Appl. Phys. Lett."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"112107","DOI":"10.1063\/1.2045551","article-title":"Selectively excited photoluminescence from Eu-implanted GaN","volume":"87","author":"Wang","year":"2005","journal-title":"Appl. Phys. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"085209","DOI":"10.1103\/PhysRevB.81.085209","article-title":"Identification of the prime optical center in GaN:Eu3+","volume":"81","author":"Roqan","year":"2010","journal-title":"Phys. Rev. B"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"204501","DOI":"10.1063\/1.4879253","article-title":"The role of donor-acceptor pairs in the excitation of Eu-ions in GaN:Eu epitaxial layers","volume":"115","author":"Mitchell","year":"2014","journal-title":"J. Appl. Phys."},{"key":"ref_13","first-page":"82620C-1","article-title":"High pressure annealing of europium implanted GaN","volume":"2012","author":"Lorenz","year":"2012","journal-title":"Proc. SPIE"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"662","DOI":"10.1002\/pssc.201300519","article-title":"Europium-doped GaN(Mg): Beyond the limits of the light-emitting diode","volume":"11","author":"Edwards","year":"2014","journal-title":"Phys. Status Solidi C"},{"key":"ref_15","unstructured":"O\u2019Donnell, K.P. (2015). 2015 UKNC Winter Meeting, University of Nottingham. Unpublished talk."},{"key":"ref_16","unstructured":"O\u2019Donnell, K.P. (2016). 2016 UKNC Winter Meeting, University of Cambridge. Unpublished talk."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/11\/10\/1800\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:22:00Z","timestamp":1760196120000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/11\/10\/1800"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,9,22]]},"references-count":16,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2018,10]]}},"alternative-id":["ma11101800"],"URL":"https:\/\/doi.org\/10.3390\/ma11101800","relation":{"has-preprint":[{"id-type":"doi","id":"10.20944\/preprints201807.0129.v1","asserted-by":"object"}]},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,9,22]]}}}