NiOx/\b{eta}-Ga2O3 Heterojunction Diode Achieving Breakdown Voltage >3 kV with Plasma Etch Field-Termination

TL;DR

This paper reports a NiOx/eta-Ga2O3 heterojunction diode with over 3 kV breakdown voltage, low leakage, and high electric fields, achieved through plasma etch field-termination, demonstrating promising high-voltage device performance.

Contribution

The work introduces a novel fabrication of NiOx/eta-Ga2O3 heterojunction diodes with record-high breakdown voltage and improved field-termination techniques, advancing high-voltage semiconductor device technology.

Findings

Breakdown voltage >3 kV on 100-μm pads

Low reverse leakage current density (~10^-8 to 10^-6 A/cm^2)

High junction electric field (>3.34 MV/cm) at 3 kV

Abstract

This work reports the fabrication and characterization of a NiOx/\b{eta}-Ga2O3 heterojunction diode (HJD) that uses a metallic nickel (Ni) target to deposit NiOx layers via reactive RF magnetron sputtering and lift-off processing with >3 kV breakdown voltage, record-low reverse current leakage under high reverse bias, and high junction electric fields (>3.34 MV/cm). The heterojunction diodes are fabricated via bilayer NiOx sputtering followed by self-aligned mesa-etching for field-termination on both large (1-mm2) and small area (100-{\mu}m diameter) devices. The HJD exhibits a ~135 A/cm2 forward current density at 5 V with a rectifying ratio of ~1010. The minimum differential specific on-resistance is measured to be 17.26 m{\Omega} cm2. The breakdown voltage on 100-{\mu}m diameter pads was measured to be greater than 3 kV with a noise floor-level reverse leakage current density (10-8~10-6 A/cm2) until 3 kV, accomplishing a parallel-plane junction electric field to be at least 3.34 MV/cm at 3 kV with a power figure of merit (PFOM) >0.52 GW/cm2. Temperature-dependent forward current density-voltage (J-V) measurements are performed from room temperature (25 C) to 200 C which showed a temperature coefficient of resistance ({\alpha}) equaling 1.56, higher than that of \b{eta}-Ga2O3 Schottky barrier diodes (SBDs), indicating potential conductivity degradation within NiOx at elevated temperatures.