Epitaxy of >7 μm Thick GaN Drift Layers on 150 mm Si(111) Substrates Realizing Vertical PN Diodes with 1200 V Breakdown Voltage

Metal-organic chemical vapor deposition growth of vertical GaN PN structures on 6″ Si(111) substrates enabling a 1200 V breakdown voltage is demonstrated. Thanks to an optimized buffer structure utilizing island growth in an AlN/Al<inf>0.1</inf>Ga<inf>0.9</inf>N superlattice, the threading dislocation density is drastically reduced, and sufficient compressive stress is incorporated in active GaN layers to compensate for the thermal mismatch. Crack-free PN structures with drift layer thicknesses up to 7.4 μm are realized with a threading dislocation density of ≈5 × 10⁸ cm⁻² and an absolute wafer bow <50 μm. Quasi-vertical PN diodes reveal a linear increase in the breakdown voltage with the drift layer thickness with an average breakdown field of ≈1.6 MV cm⁻¹. Additionally, the leakage current is shown to decrease monotonically as the drift layer thickness increases. For a 7.4 μm thick drift layer with a net ionized donor concentration of 0.9 × 10¹⁶ cm⁻³, a high breakdown voltage of 1200 V, a low specific on-resistance of 0.4 mΩ cm⁻², and a low leakage current of 10⁻⁴ A cm⁻² (at a reverse bias of 650 V) are obtained. These results demonstrate the great potential of cost-effective vertical GaN-on-Si power devices operating in the kilovolt range.