kV-Class Lateral NiOx/GaN Super-Heterojunction Diode via Ammonia Molecular Beam Epitaxy (NH3-MBE)

TL;DR

This paper demonstrates lateral NiOx/GaN super-heterojunction diodes with high breakdown voltage and low leakage, utilizing ammonia molecular beam epitaxy to achieve charge-balanced structures and superjunction effects on GaN layers.

Contribution

It introduces a novel lateral super-heterojunction diode structure using NiOx and GaN with charge balancing, showing significant performance improvements over traditional structures.

Findings

Achieved a maximum breakdown voltage of ~2.8 kV.

Demonstrated a 6-fold increase in breakdown voltage compared to reference structures.

Exhibited ultra-low reverse leakage current and high rectification ratio.

Abstract

This work reports the demonstration of lateral p-NiOx/p-GaN/n-GaN-based super-heterojunction (SHJ) diodes using p-GaN with additional sputtered p-type nickel oxide (NiOx) layers to realize charge-balanced structures. The heterojunction diode capacitance-voltage (C-V) model is applied to extract effective the acceptor concentration from the p-NiOx. Net donor and acceptor concentration in n-GaN and p-GaN are extracted by using metal-oxide-semiconductor (MOS) test structures. The fabricated p-NiOx/p-GaN/n-GaN SHJ diodes with charge-balanced region between anode and cathode exhibit a forward on-state current density of 10-30 mA/mm across an anode-to-cathode distance (LAC) from 16 {\mu}m to 80 {\mu}m. The SHJ diodes show rectifying behavior with a maximum on/off ratio of 10^9 and a low reverse leakage density. The highest breakdown voltage achieved for the SHJ diodes is ~2.8 kV with reverse leakage density of 10^-4 mA/mm at ~80% of devices catastrophic breakdown voltage. The SHJ diodes across all types of dimensions exhibit significant breakdown voltage improvements (~6X on average) with ultra-low reverse leakage current compared to corresponding reference structures without a charge-balanced extension, clearly demonstrating the superjunction effect for devices fabricated on GaN epitaxial layer with ~10^17 cm^-3 electron density.