Extraction of stress and dislocation density using in-situ curvature measurements for AlGaN and GaN on silicon growth
Résumé
We have analyzed the in-situ measurements of bow and reflectance during growth of GaN on silicon layers for HEMT based devices, varying the quality of the layers by changing the AlN nucleation layer. By fitting the curves and applying the Stoney equation, we were able to extract stress profiles in the layers, and convert these into out of plane strain profiles. This allowed us to simulate X-Ray Diffraction profiles which matched well with measured data, confirming the validity of our data extraction. Finally, we see that we incorporate less stress with a higher dislocation density in the GaN layers, and so for a given set of growth conditions, we can infer the dislocation density by looking a the relaxation rate.
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