News – 08/01/2025

Vol.6 of EpiNet®’s "Algorithm Deep-Dive" series

Getting the best out of your LayTec data: Learn how to analyze your in-situ data most efficiently

Welcome back to our "Algorithm Deep-Dive" series. Here, we regularly introduce one of LayTec’s advanced in-situ algorithms featured in our EpiNet® software on LinkedIn. The series is meant to help you to fully exploit the possibilities of EpiNet® to the benefit of your epi process.

Please feel free to contact our support team via info@laytec.de for further introduction during a dedicated EpiNet® training or to receive sample data for exploring the possibilities of EpiNet®’s algorithms on your own.

Today, in the series’ sixth volume, the "MultiWL Composition Fit" is introduced.

For the the "MultiWL Composition Fit" algorithm multiple reflectance wavelengths can be chosen from the database (typically 405 nm, 633 nm, 950 nm, but others are available as well) to determine the composition of a growing layer more robustly and precisely. Each wavelength carries different sensitivity for refractive index and absorption – combining them enhances confidence in fitting results.

This can be particularly helpful when analyzing thin layers. In such cases, only a small fraction of the oscillation can be recorded during deposition. By using multiple wavelengths with the "MultiWL Composition Fit", the quality and robustness of the analysis are significantly improved, even when only limited data is available for fitting.

Fig. 1: Analysis screen of EpiNet® applying the "MultiWL Composition fit" allowing for deducing the layer composition by fitting all three (or two) wavelengths transients. Here, the algorithm was applied to a AlGaN growth run where the respective values of n and k were taken from the EpiNet® database. Note that in this example more oscillation as shown here were measured and fitted subsequently for this AlGaN layer.
Fig. 2: Results window displaying the fit results (X=0.787) for the composition of Al(X)Ga(X-1)N. Note that a substrate reflection correction was applied prior to fittig to improve the quality of the fit results.

Usage ideas and alternatives:

  • More reliable composition extraction from complex in-situ transients

  • Particularly suited for lattice-matched material systems with known nk data (e.g. AlGaAs)

  • More accurate and robust results results than single-wavelength fits

Limitations:

  • The Fit is currently limited to 3 input wavelengths (but can be manually extended)

  • Requires accurate nk values and similar optical path for all inputs

  • Not suitable for strongly absorbing or tilted measurements without further correction

Curious about the details? User instructions can be found in the manual and can be obtained via info@laytec.de. Reference data is available in EpiNet®

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