Design and development of 1.5 kV vertical GaN pn diodes on HVPE substrate

We report the design and development of vertical 1.5 kV GaN p–n diodes that consists of an 8 μm drift layer and a thin p-GaN/p+-GaN layer grown by metal–organic chemical vapor deposition (MOCVD) on a hydride vapor phase epitaxy (HVPE) synthesized GaN substrate. The drift layer has a low doping concentration of ∼9 × 1015 cm−3 and electron mobility ~ 1200 cm2/Vs at room temperature. The fabricated devices with an optimized guard ring design as edge termination exhibit a breakdown voltage of > 1.5 kV with specific on-resistance of ~ 1.5 mΩ cm2. The breakdown efficiency of these diodes is over 72% when compared to ideal analytical calculations and over 90% with respect to numerical simulations. Temperature-dependent measurements show that the devices have a positive temperature coefficient suggesting the avalanche breakdown mechanism. These results suggest that these MOCVD grown vertical GaN-on-GaN (HVPE) p–n diodes are promising for low-mid range voltage power switching applications.