Composition determination of quaternary GaAsPN layers from single XRD measurement of quasi-forbidden (002) reflection

TL;DR

This study demonstrates that single XRD measurement of the (002) reflection can effectively determine the composition of GaAsPN quaternary layers, offering a quick alternative to more complex methods, with some limitations related to nitrogen content and layer thickness.

Contribution

The paper introduces a novel XRD-based method for full composition determination of GaAsPN layers using a single measurement of the quasi-forbidden (002) reflection.

Findings

The method accurately estimates arsenic and nitrogen content within specified error margins.

The accuracy decreases with increasing nitrogen content and layer thickness due to crystal quality issues.

Comparison with Rutherford backscattering confirms the method's validity within certain limits.

Abstract

GaAsPN layers with a thickness of 30nm were grown on GaP substrates with metalorganic vapor phase epitaxy to study the feasibility of a single X-ray diffraction (XRD) measurement for full composition determination of quaternary layer material. The method is based on the peak intensity of a quasi-forbidden (002) reflection which is shown to vary with changing arsenic content for GaAsPN. The method works for thin films with a wide range of arsenic contents and shows a clear variation in the reflection intensity as a function of changing layer composition. The obtained thicknesses and compositions of the grown layers are compared with accurate reference values obtained by Rutherford backscattering spectroscopy combined with nuclear reaction analysis measurements. Based on the comparison, the error in the XRD defined material composition becomes larger with increasing nitrogen content and layer thickness. This suggests that the dominating error source is the deteriorated crystal quality due to the nonsubstitutional incorporation of nitrogen into the crystal lattice and strain relaxation. The results reveal that the method overestimates the arsenic and nitrogen content within error margins of about 0.12 and about 0.025, respectively.