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Structural and Optical Effects of Capping Layer Material and Growth Rate on the Properties of Self-Assembled InAs Quantum Dot Structures

Published online by Cambridge University Press:  26 February 2011

Gabriel Agnello ,
Vadim Tokranov ,
Michael Yakimov ,
Matthew Lamberti ,
Yuegui Zheng  and
Serge Oktyabrsky
Gabriel Agnello
Affiliation:
College of Nanoscale Science and Engineering, University at Albany – SUNY, 251 Fuller Road, Albany, NY 12203, U.S.A.
Vadim Tokranov
Affiliation:
College of Nanoscale Science and Engineering, University at Albany – SUNY, 251 Fuller Road, Albany, NY 12203, U.S.A.
Michael Yakimov
Affiliation:
College of Nanoscale Science and Engineering, University at Albany – SUNY, 251 Fuller Road, Albany, NY 12203, U.S.A.
Matthew Lamberti
Affiliation:
College of Nanoscale Science and Engineering, University at Albany – SUNY, 251 Fuller Road, Albany, NY 12203, U.S.A.
Yuegui Zheng
Affiliation:
College of Nanoscale Science and Engineering, University at Albany – SUNY, 251 Fuller Road, Albany, NY 12203, U.S.A.
Serge Oktyabrsky
Affiliation:
College of Nanoscale Science and Engineering, University at Albany – SUNY, 251 Fuller Road, Albany, NY 12203, U.S.A.
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Abstract

In order to develop nanoengineering methods to control electronic spectrum of self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy, we have utilized atomic force microscopy (AFM), photoluminescence (PL) and TEM methods to investigate the effects of capping layer growth on the physical/chemical properties as well as the optical/electronic performance of QD device structures. Capping layer material choice (or its absence all together) has been found to directly influence QD dimensions (size, height), and subsequently, to affect QD emission wavelength. We report results of QD lateral size and height as well as densities of InAs QDs capped with 2ML (monolayers) of AlAs or GaAs grown at various rates. Our AFM results are complemented by PL measurements, where the optical properties of capped versus non-capped QDs have been explored and direct correspondence between structural differences induced by capping and the electronic/optical properties of QDs is demonstrated. Analysis of the data shows that the results can be explained by two competing surface processes. The first of which is the redistribution of indium between QDs on top of the 2D wetting layer, resulting in the increase of QD size with time. The second effect is the diffusion of indium out of the QDs and onto the top of the capping layer. TEM with multislice image simulation has supported our AFM and PL observations with the demonstration of “indium driven” alloy intermixing in the overlayer as well as significant alloying in the InAs wetting layer.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 829: Symposium B – Progress in Compound Semiconductor Materials IV – Electronic and Optoelectronic Applications , 2004 , B2.1
Copyright
Copyright © Materials Research Society 2005

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References

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