Quantification of trace-level silicon doping in AlxGa1–xN films using wavelength-dispersive X-ray microanalysis

Spasevski, Lucia and Buse, Ben and Edwards, Paul R. and Hunter, Daniel A. and Enslin, Johannes and Foronda, Humberto M. and Wernicke, Tim and Mehnke, Frank and Parbrook, Peter J. and Kneissl, Michael and Martin, Robert W. (2021) Quantification of trace-level silicon doping in AlxGa1–xN films using wavelength-dispersive X-ray microanalysis. Microscopy and Microanalysis, 27 (4). pp. 696-704. ISSN 1431-9276 (https://doi.org/10.1017/S1431927621000568)

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Wavelength dispersive X-ray (WDX) spectroscopy was used to measure silicon atom concentrations in the range 35–100 ppm (corresponding to (3–9) ×1018 cm-3) in doped AlxGa1–xN films using an electron probe microanalyser also equipped with a cathodoluminescence (CL) spectrometer. Doping with Si is the usual way to produce the n-type conducting layers that are critical in GaN and AlxGa1–xN-based devices such as LEDs and laser diodes. Previously we have shown excellent agreement for Mg dopant concentrations in p-GaN measured by WDX with values from the more widely used technique of secondary ion mass spectrometry (SIMS). However, a discrepancy between these methods has been reported when quantifying the n-type dopant, silicon. We identify the cause of discrepancy as inherent sample contamination and propose a way to correct this using a calibration relation. This new approach, using a method combining data derived from SIMS measurements on both GaN and AlxGa1–xN samples, provides the means to measure the Si content in these samples with account taken of variations in the ZAF corrections. This method presents a cost effective and time saving way to measure the Si doping and can also benefit from simultaneously measuring other signals, such as CL and electron channeling contrast imaging.


Spasevski, Lucia ORCID logoORCID: https://orcid.org/0000-0002-7409-3807, Buse, Ben, Edwards, Paul R. ORCID logoORCID: https://orcid.org/0000-0001-7671-7698, Hunter, Daniel A., Enslin, Johannes, Foronda, Humberto M., Wernicke, Tim, Mehnke, Frank, Parbrook, Peter J., Kneissl, Michael and Martin, Robert W. ORCID logoORCID: https://orcid.org/0000-0002-6119-764X;