Evidence of a second acceptor state of the E center in Si1-x Gex

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© 2007 American Physical Society (APS). This is the accepted version of the following article: Kuitunen, K. & Tuomisto, Filip & Slotte, J. 2007. Evidence of a second acceptor state of the E center in Si1-x Gex. Physical Review B. Volume 76, Iss, which has been published in final form http://journals.aps.org/prb/abstract/10.1103/PhysRevB.76.233202.
Journal Title
Journal ISSN
Volume Title
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2007
Major/Subject
Mcode
Degree programme
Language
en
Pages
233202/1-4
Series
Physical Review B, Volume 76, Issue 23
Abstract
We have found evidence of a second acceptor state of the E center in Si1-x Gex by using positron annihilation spectroscopy. To achieve this, we studied proton irradiated n-type Si1−x Gex with a Ge content of 10%–30% and a P dopant concentration of 10 exp 18cm exp −3, in which the number of Ge atoms around irradiation induced E centers was increased by annealing. When measuring the Doppler broadening of the annihilation line, the shape parameter S starts to decrease at 150 K with decreasing measurement temperature. This indicates that a charge transition in the upper half of the Si1−x Gex band gap, above the well known (0/−) level, takes place. Hence, we suggest that the increased concentration of germanium around the E center pulls down the localized second acceptor state into the Si1−x Gex band gap, making the Ge decorated E center a more effective trap for conduction electrons.
Description
Keywords
E center, vacancies, Silicon germanium, acceptor state, positron annihilation spectroscopy
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Citation
Kuitunen, K. & Tuomisto, Filip & Slotte, J. 2007. Evidence of a second acceptor state of the E center in Si1-x Gex. Physical Review B. Volume 76, Issue 23. 233202/1-4. ISSN 1098-0121 (printed). DOI: 10.1103/physrevb.76.233202