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Secondary Electron Emission Contrast of Quantum Wells in GaAs p-i-n Junctions

Published online by Cambridge University Press:  16 March 2009

Enrique Grunbaum ,
Zahava Barkay ,
Yoram Shapira ,
Keith W.J. Barnham ,
David B. Bushnell ,
Nicholas J. Ekins-Daukes ,
Massimo Mazzer  and
Peter Wilshaw
Enrique Grunbaum*
Affiliation:
Department of Physical Electronics, Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel
Zahava Barkay
Affiliation:
Wolfson Applied Materials Research Centre, Tel-Aviv University, Tel-Aviv 69978, Israel
Yoram Shapira
Affiliation:
Department of Physical Electronics, Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel
Keith W.J. Barnham
Affiliation:
Department of Physics, Imperial College of Science, Technology & Medicine, London SW7 2BW, UK
David B. Bushnell
Affiliation:
Department of Physics, Imperial College of Science, Technology & Medicine, London SW7 2BW, UK
Nicholas J. Ekins-Daukes
Affiliation:
Department of Physics, Imperial College of Science, Technology & Medicine, London SW7 2BW, UK
Massimo Mazzer
Affiliation:
Department of Physics, Imperial College of Science, Technology & Medicine, London SW7 2BW, UK
Peter Wilshaw
Affiliation:
Department of Materials, Parks Road, University of Oxford, Oxford OK1 3PH, UK
*
Corresponding author. E-mail: enrique@eng.tau.ac.il
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Abstract

The secondary electron (SE) signal over a cleaved surface of GaAs p-i-n solar cells containing stacks of quantum wells (QWs) is analyzed by high-resolution scanning electron microscopy. The InGaAs QWs appear darker than the GaAsP barriers, which is attributed to the differences in electron affinity. This method is shown to be a powerful tool for profiling the conduction band minimum across junctions and interfaces with nanometer resolution. The intrinsic region is shown to be pinned to the Fermi level. Additional SE contrast mechanisms are discussed in relation to the dopant regions themselves as well as the AlGaAs window at the p-region. A novel method of in situ observation of the SE profile changes resulting from reverse biasing these structures shows that the built-in potential may be deduced. The obtained value of 0.7 eV is lower than the conventional bulk value due to surface effects.

Keywords

high-resolution scanning electron microscopysecondary electronsquantum wellsconductance bandvalence banddopant contrastGaAs
Type
Materials Applications
Information
Microscopy and Microanalysis , Volume 15 , Issue 2 , April 2009 , pp. 125 - 129
Copyright
Copyright © Microscopy Society of America 2009

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References

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