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Influence of the local environment on Mn acceptors in GaAs
This content has been downloaded from IOPscience. Please scroll down to see the full text. 2015 J. Phys.: Condens. Matter 27 154202 (http://iopscience.iop.org/0953-8984/27/15/154202) View the table of contents for this issue, or go to the journal homepage for more
Download details: IP Address: 149.171.67.164 This content was downloaded on 01/09/2015 at 20:40
Please note that terms and conditions apply.
Journal of Physics: Condensed Matter J. Phys.: Condens. Matter 27 (2015) 154202 (8pp)
doi:10.1088/0953-8984/27/15/154202
Influence of the local environment on Mn acceptors in GaAs Donghun Lee1 , David Gohlke2 , Anne Benjamin and Jay A Gupta Department of Physics, Ohio State University, Columbus, OH 43210, USA E-mail: [email protected] Received 21 August 2014, revised 9 November 2014 Accepted for publication 12 November 2014 Published 18 March 2015 Abstract
As transistors continue to shrink toward nanoscale dimensions, their characteristics are increasingly dependent on the statistical variations of impurities in the semiconductor material. The scanning tunneling microscope (STM) can be used to not only study prototype devices with atomically precise placement of impurity atoms, but can also probe how the properties of these impurities depend on the local environment. Tunneling spectroscopy of Mn acceptors in GaAs indicates that surface-layer Mn act as a deep acceptor, with a hole binding energy that can be tuned by positioning charged defects nearby. Band bending induced by the tip or by these defects can also tune the ionization state of the acceptor complex, evident as a ring-like contrast in STM images. The interplay of these effects is explored over a wide range of defect distances, and understood using iterative simulations of tip-induced band bending. Keywords: scanning tunneling microscopy, tip-induced band bending, dopants, scanning tunneling spectroscopy, adatoms, ionization (Some figures may appear in colour only in the online journal)
edges [20], other dopants [16], native defects [17] or surface adsorbates [21, 22]. These environmental factors may already limit the reproducibility of current transistors, and may provide avenues for decoherence or spin relaxation in next-generation devices. Recent advances combining STM with other scanned probe and optical methods suggest a new era in developing an atomistic understanding and control over impurities and defects in semiconductors [23, 24]. Here we provide a snapshot of current research into how the local environment influences the properties of individual dopants in GaAs. Tunneling spectra reveal a rich variety of phenomena, but the complex role of band bending induced by the STM tip must be considered carefully in the interpretation. We find that proximity of these dopants to the vacuum interface and to other defects can not only increase the carrier binding energy by ∼7×, but can also influence the ionization state and coupling to the host bands [14, 17, 21, 25, 26].
1. Introduction
As transistors shrink to nanoscale dimensions, their characteristics depend less on average semiconductor material properties and more on the number and arrangement of defects [1–4]. Broadly defined, defects may be impurities intentionally added to modify the conductivity (i.e. dopants), native defects (vacancies, interstitials, antisites) and complexes with varying spatial organization. The emerging field of ‘solotronics’, where individual defects in semiconductors are used as the medium for information storage and processing [5], has promise for extending conventional transistors to the nanoscale regime, as well as next-generation quantum or spin-based devices [6–9]. Toward these ends, the scanning tunneling microscope (STM) has been used to prepare devices with atomically precise placement of phosphorous dopants [10, 11], and tune dopant properties via tip-induced fields [12–15], or by tuning the interactions with other defects [16, 17]. The STM can also be used to probe the dependence of dopant properties on local environmental factors such as proximity to the bulk/vacuum interface [18, 19], step
2. Methods 2.1. Scanning tunneling microscopy and spectroscopy
1
Present address: Department of Physics, University of California, Santa Barbara, CA 93106, USA. 2 Present address: Institut f¨ ur Experimentelle und Angewandte Physik, University of Regensburg, D-93053 Regensburg, Germany. 0953-8984/15/154202+08$33.00
Experiments were conducted with two low-temperature STMs, operating in a cryogenic (
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My IOPscience
Influence of the local environment on Mn acceptors in GaAs
This content has been downloaded from IOPscience. Please scroll down to see the full text. 2015 J. Phys.: Condens. Matter 27 154202 (http://iopscience.iop.org/0953-8984/27/15/154202) View the table of contents for this issue, or go to the journal homepage for more
Download details: IP Address: 149.171.67.164 This content was downloaded on 01/09/2015 at 20:40
Please note that terms and conditions apply.
Journal of Physics: Condensed Matter J. Phys.: Condens. Matter 27 (2015) 154202 (8pp)
doi:10.1088/0953-8984/27/15/154202
Influence of the local environment on Mn acceptors in GaAs Donghun Lee1 , David Gohlke2 , Anne Benjamin and Jay A Gupta Department of Physics, Ohio State University, Columbus, OH 43210, USA E-mail: [email protected] Received 21 August 2014, revised 9 November 2014 Accepted for publication 12 November 2014 Published 18 March 2015 Abstract
As transistors continue to shrink toward nanoscale dimensions, their characteristics are increasingly dependent on the statistical variations of impurities in the semiconductor material. The scanning tunneling microscope (STM) can be used to not only study prototype devices with atomically precise placement of impurity atoms, but can also probe how the properties of these impurities depend on the local environment. Tunneling spectroscopy of Mn acceptors in GaAs indicates that surface-layer Mn act as a deep acceptor, with a hole binding energy that can be tuned by positioning charged defects nearby. Band bending induced by the tip or by these defects can also tune the ionization state of the acceptor complex, evident as a ring-like contrast in STM images. The interplay of these effects is explored over a wide range of defect distances, and understood using iterative simulations of tip-induced band bending. Keywords: scanning tunneling microscopy, tip-induced band bending, dopants, scanning tunneling spectroscopy, adatoms, ionization (Some figures may appear in colour only in the online journal)
edges [20], other dopants [16], native defects [17] or surface adsorbates [21, 22]. These environmental factors may already limit the reproducibility of current transistors, and may provide avenues for decoherence or spin relaxation in next-generation devices. Recent advances combining STM with other scanned probe and optical methods suggest a new era in developing an atomistic understanding and control over impurities and defects in semiconductors [23, 24]. Here we provide a snapshot of current research into how the local environment influences the properties of individual dopants in GaAs. Tunneling spectra reveal a rich variety of phenomena, but the complex role of band bending induced by the STM tip must be considered carefully in the interpretation. We find that proximity of these dopants to the vacuum interface and to other defects can not only increase the carrier binding energy by ∼7×, but can also influence the ionization state and coupling to the host bands [14, 17, 21, 25, 26].
1. Introduction
As transistors shrink to nanoscale dimensions, their characteristics depend less on average semiconductor material properties and more on the number and arrangement of defects [1–4]. Broadly defined, defects may be impurities intentionally added to modify the conductivity (i.e. dopants), native defects (vacancies, interstitials, antisites) and complexes with varying spatial organization. The emerging field of ‘solotronics’, where individual defects in semiconductors are used as the medium for information storage and processing [5], has promise for extending conventional transistors to the nanoscale regime, as well as next-generation quantum or spin-based devices [6–9]. Toward these ends, the scanning tunneling microscope (STM) has been used to prepare devices with atomically precise placement of phosphorous dopants [10, 11], and tune dopant properties via tip-induced fields [12–15], or by tuning the interactions with other defects [16, 17]. The STM can also be used to probe the dependence of dopant properties on local environmental factors such as proximity to the bulk/vacuum interface [18, 19], step
2. Methods 2.1. Scanning tunneling microscopy and spectroscopy
1
Present address: Department of Physics, University of California, Santa Barbara, CA 93106, USA. 2 Present address: Institut f¨ ur Experimentelle und Angewandte Physik, University of Regensburg, D-93053 Regensburg, Germany. 0953-8984/15/154202+08$33.00
Experiments were conducted with two low-temperature STMs, operating in a cryogenic (
