GaN Metal-organic Vapor Phase Epitaxy on Sc2O3/Si Templates for Group III-nitride Monolithic Integration to Si Technology

In this work, we present a detailed analysis of GaN layers up to 500 nm thick, directly grown on Sc2O3(111)/Si(111) templates using metal-organic vapor phase epitaxy (MOVPE). A range of measurement techniques, including X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), cathodoluminescence, and scanning electron microscopy (SEM), were used to evaluate structural quality, strain/stress states, surface morphology, and dislocation densities. The micro-stripe formation was observed when the growth was conducted in a nitrogen atmosphere, with the stripes completely disappearing when the growth atmosphere was switched to hydrogen. The stripes were determined to be of a cubic GaN phase. The epitaxial relationships between the cubic GaN crystalline lattice and Sc2O3, Si, and hexagonal GaN were examined in detail. Continuous, c-axis-oriented, monocrystalline GaN layers on Sc2O3 can be achieved in both N2 and H2 atmospheres. Prolonged nitridation processes of up to 1200 seconds improved the smoothness and crystallinity of the GaN layers, significantly reducing the number of extended defects. Switching the growth atmosphere from N2 to H2 led to reduced dislocation densities, minimized cubic GaN formation, and improved the surface morphology of the GaN layers. Our analysis shows that due to the lattice and thermal mismatch between GaN and the Si substrate, the GaN layers experience tensile strain. To manage this strain, AlxGa1-xN interlayers were inserted after 100 nm of GaN growth. This strain-engineering approach resulted in smooth, crack-free GaN epitaxial layers, demonstrating the potential for integrating GaN into silicon technology using a Sc2O3.