Crystal Growth Design for Bowing Mitigation in Thick AlGaN Layers on GaN Substrates

Thick aluminum gallium nitride (AlGaN) drift layers are critical for achieving high breakdown voltages in next-generation energy-efficient vertical power devices. However, their growth on GaN substrates induces substantial tensile stress, resulting in pronounced concave bowing that can compromise structural integrity and device performance. In this study, we demonstrate a crystal growth and epitaxial design strategy to control curvature in 5 μm-thick AlGaN drift layers with 6% aluminum grown by metal–organic chemical vapor deposition. By introducing a backside N-polar AlGaN compensation layer and an n+-GaN interlayer, the curvature was reduced from −0.27 to −0.065 m–1, approaching the as-received substrate values. This bowing-engineering approach was successfully applied to both hydride vapor phase epitaxy and ammonothermal GaN substrates, highlighting its generality. The methodology provides a scalable route for strain and curvature management in AlGaN/GaN heterostructures, supporting the design and fabrication of high-breakdown-voltage devices with optimized structural and electronic performance.