Strain-inversion Strategy Achieving 53μm-ultra-thick, Stress-free III-nitride Heteroepitaxy by MOCVD

As the semiconductor industry increasingly pivots toward "More than Moore" and "More Moore" paradigms, heterogeneous integration has emerged as a pivotal strategy for achieving system-level performance breakthroughs. However, the residual stress inherent in integrating dissimilar materials represents a critical bottleneck, directly threatening the integrity and reliability of these advanced systems. Heteroepitaxy, serving as a representative example, is inherently constrained by stress accumulation, which limits epilayer thickness, increases threading dislocation density (TDD), and degrades device reliability. Here, we present a strain-inversion strategy that effectively transfers the misfit-induced stress from the epilayer into the substrate stack. Through co-designed theoretical modeling and experimental validation, we demonstrate the metalorganic chemical vapor deposition (MOCVD) growth of 53-µm-thick, stress-free heteroepitaxial GaN films, exhibiting outstanding structural quality with X-ray rocking curve full-width-at-half-maxima (FWHM) of 83 and 119 arcsec for the (002) and (102) planes, respectively, and a TDD as low as 5×10⁷ cm⁻². These results not only set a new thickness record for MOCVD-grown heteroepitaxial GaN but also achieve the crystal quality comparable to state-of-the-art benchmarks. Our approach establishes strain-inverted epitaxy as a highly promising platform for high-performance nitride devices and paves the way for producing low-cost and strain-free GaN and AlN substrates.