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Crystals 2018, 8(11), 437; https://doi.org/10.3390/cryst8110437

Interfacial Mixing Analysis for Strained Layer Superlattices by Atom Probe Tomography

1
Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
2
Department of Material Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
3
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
4
Intraband LLC, 505 S. Rosa Road, Suite 34, Madison, WI 53719, USA
*
Author to whom correspondence should be addressed.
Received: 30 October 2018 / Revised: 17 November 2018 / Accepted: 18 November 2018 / Published: 21 November 2018
(This article belongs to the Special Issue MOVPE Growth of Crystalline Film)
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Abstract

Quantum wells and barriers with precise thicknesses and abrupt composition changes at their interfaces are critical for obtaining the desired emission wavelength from quantum cascade laser devices. High-resolution X-ray diffraction and transmission electron microscopy are commonly used to calibrate and characterize the layers’ thicknesses and compositions. A complementary technique, atom probe tomography, was employed here to obtain a direct measurement of the 3-dimensional spatially-resolved compositional profile in two InxGa1−xAs/InyAl1−yAs III-V strained-layer superlattice structures, both grown at 605 °C. Fitting the measured composition profiles to solutions to Fick’s Second Law yielded an average interdiffusion coefficient of 3.5 × 10−23 m2 s−1 at 605 °C. The extent of interdiffusion into each layer determined for these specific superlattices was 0.55 nm on average. The results suggest that quaternary active layers will form, rather than the intended ternary compounds, in structures with thicknesses and growth protocols that are typically designed for quantum cascade laser devices. View Full-Text
Keywords: superlattice; quantum cascade lasers; metalorganic vapor phase epitaxy; semiconducting III-V materials; atom probe tomography superlattice; quantum cascade lasers; metalorganic vapor phase epitaxy; semiconducting III-V materials; atom probe tomography
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Rajeev, A.; Chen, W.; Kirch, J.D.; Babcock, S.E.; Kuech, T.F.; Earles, T.; Mawst, L.J. Interfacial Mixing Analysis for Strained Layer Superlattices by Atom Probe Tomography. Crystals 2018, 8, 437.

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