Characterization Of Multi-Layered AlGaAs Structures Using X-Ray Diffraction And Optical Reflectometry

Marten Walther; Karl J. Ebeling; Peter Becker; Jurgen Stumpel

doi:10.1117/12.949459

11 April 1989 Characterization Of Multi-Layered AlGaAs Structures Using X-Ray Diffraction And Optical Reflectometry

Marten Walther, Karl J. Ebeling, Peter Becker, Jurgen Stumpel

Proceedings Volume 1015, Micromachining Optical Components and Precision Engineering; (1989) https://doi.org/10.1117/12.949459
Event: 1988 International Congress on Optical Science and Engineering, 1988, Hamburg, Germany

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.

Citation Download Citation

Marten Walther, Karl J. Ebeling, Peter Becker, and Jurgen Stumpel "Characterization Of Multi-Layered AlGaAs Structures Using X-Ray Diffraction And Optical Reflectometry", Proc. SPIE 1015, Micromachining Optical Components and Precision Engineering, (11 April 1989); https://doi.org/10.1117/12.949459

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KEYWORDS

Gallium arsenide

Superlattices

Diffraction

X-ray diffraction

Dielectrics

X-ray optics

Gallium

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