1 μm C-Doped GaN Thin Buffer on Sapphire with >3 kV Lateral Breakdown Voltage Grown by MOCVD

Sapphire-based GaN buffers face inherent challenges from the lattice mismatch between GaN and sapphire, which leads to high threading dislocation density and limits lateral breakdown voltage. In this work, we investigated the optimization of metal–organic chemical vapor deposition (MOCVD) growth parameters—specifically carbon doping concentration, GaN buffer thickness, AlN nucleation layer thickness, growth pressure and V/III ratio—to enhance crystal quality and breakdown performance. A sapphire-based C-doped GaN buffer layer was successfully fabricated exhibiting a lateral breakdown voltage exceeding 3000 V across a 30 μm electrode gap corresponding to an average breakdown electric field of approximately 1.0 MV/cm, accompanied by low threading dislocation density, excellent surface roughness and low leakage currents. This study provides technical insights and practical growth guidelines for high-voltage sapphire-based GaN buffer layers, establishing the material basis for future high-voltage power device applications.