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Proceedings Paper

Characterization Of Multi-Layered AlGaAs Structures Using X-Ray Diffraction And Optical Reflectometry
Author(s): Marten Walther; Karl J. Ebeling; Peter Becker; Jurgen Stumpel
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Paper Abstract

Recently, we have developed efficient optically controllable modulators in AlGaAs that apply band filling or electroabsorption. These reflection modulators typically consist of a GaA1As multi-quantum well (MQW) structure in front of a multi-layered AlGaAs dielectric reflector. Optimizing the performance of the devices requires a precise control of layer thickness and material composition. For analysis of the epilayers grown by molecular beam epitaxy we employ optically reflectometry and X-ray diffraction. Correlating optically measured reflection spectra and numerically computed reflection curves we obtain the optical thickness of individual layers. A simple evaluation method provides resolution of a few nanometers when the periodicity of the structure is larger than 100 nm. For the X-ray studies we employ a double-crystal diffractometer with a germanium-monochromator. From the angular difference of the rocking curves from layer and substrate we determine the layer composition. From the fine structure of the diffraction pattern we can evaluate the thickness of the layers in composed structures. The measurement range is from less than 20 nm to 500 nm allowing for quantum wells to be investigated. In the overlapping range from 100 nm to 500 nm optical and X-ray measurements agree very well and can be used to determine the refractive index. In conclusion, the combination of X-ray diffraction and optical reflectometry provides a powerful tool for characterizing multilayered material systems of optoelectronic and optical applications.

Paper Details

Date Published: 11 April 1989
PDF: 8 pages
Proc. SPIE 1015, Micromachining Optical Components and Precision Engineering, (11 April 1989); doi: 10.1117/12.949459
Show Author Affiliations
Marten Walther, Techn. Univ. of Braunschweig (Federal Republic of Germany)
Karl J. Ebeling, Techn. Univ. of Braunschweig (Federal Republic of Germany)
Peter Becker, Physikalisch-Technische Bundesanstalt Braunschweig (Federal Republic of Germany)
Jurgen Stumpel, Physikalisch-Technische Bundesanstalt Braunschweig (Federal Republic of Germany)

Published in SPIE Proceedings Vol. 1015:
Micromachining Optical Components and Precision Engineering
Peter Langenbeck, Editor(s)

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