kV-class lateral NiOx/GaN superjunction diode via ammonia molecular beam epitaxy (NH3-MBE)

This study reports the demonstration of lateral p-NiOx/p-GaN/n-GaN-based superjunction (SJ) diodes using p-GaN with additional sputtered p-type nickel oxide (NiOx) layers to realize charge-balanced structures. The SJ diode capacitance–voltage (C–V) model is applied to extract the effective acceptor concentration from the p-NiOx. Net donor and acceptor concentrations in n-GaN and p-GaN are extracted by using metal-oxide-semiconductor test structures. The fabricated p-NiOx/p-GaN/n-GaN SJ diodes with a charge-balanced region between the anode and cathode exhibit a forward on-state current density of 10–30 mA/mm across an anode-to-cathode distance (LAC) from 16 to 80 µm. The SJ diodes show rectifying behavior with a maximum on/off ratio of 109 and a low reverse leakage density. The highest breakdown voltage achieved for the SJ diodes is ∼2.8 kV with a reverse leakage density of 10−4 mA/mm at ∼80% of the device’s catastrophic breakdown voltage. The SJ diodes across all types of dimensions exhibit significant breakdown voltage improvements (∼6× on average) with ultra-low reverse leakage current compared to corresponding reference structures without a charge-balanced extension, clearly demonstrating the SJ effect for devices fabricated on a GaN epitaxial layer with ∼1017 cm−3 electron density.