Quasi-Vertical $\beta$-Ga$_2$O$_3$ Schottky Diodes on Sapphire Using All-LPCVD Growth and Plasma-Free Ga-Assisted Etching

TL;DR

This paper reports the fabrication of high-quality quasi-vertical beta-Ga2O3 Schottky diodes on sapphire using an all-LPCVD, plasma-free process, demonstrating excellent electrical performance and potential for power electronics.

Contribution

It introduces a novel all-LPCVD, plasma-free method for growing and etching beta-Ga2O3 on sapphire, enabling high-performance Schottky diodes with improved electrical characteristics.

Findings

High-quality beta-Ga2O3 layers grown on sapphire with low defect density.

Diodes exhibit low turn-on voltage and high current density.

Breakdown voltages up to 100 V with high electric fields.

Abstract

This work demonstrates quasi-vertical beta-Ga2O3 Schottky barrier diodes (SBDs) fabricated on c-plane sapphire using an all-LPCVD, plasma-free process integrating epitaxial growth of high-quality beta-Ga2O3 and in-situ Ga-assisted etching. A 6.3 micron-thick (-201)-oriented beta-Ga2O3 layer was grown on c-sapphire with a 6-degree miscut, comprising a 3.15 micron moderately doped (2.1e17 cm^-3) drift layer and a heavily doped (1e19 cm^-3) contact layer on a UID buffer. Mesa isolation used Ga-assisted LPCVD etching, producing a 60{\deg} inclined mesa sidewalls with an etch depth of 3.6 micron. SBDs showed excellent forward J-V behavior: 1.22 V turn-on, 1.29 ideality factor, and 0.83 eV barrier height. Minimum differential specific on-resistance was 8.6 mOhm*cm^2 with high current density (252 A/cm^2 at 5 V). C-V profiling revealed uniform doping at 2.1e17 cm^-3. J-V-T from 25 C to 250 C confirmed thermionic emission. Barrier height increased from 0.80 to 1.16 eV, and ideality factor from 1.31 to 1.42. Reverse leakage current remained low, increasing from ~5e-6 A/cm^2 to ~1e-4 A/cm^2; Ion/Ioff decreased from ~1e7 to 5e5. Breakdown voltages with moderately doped (2.1e17 cm^-3) drift layer ranged between 73 and 100 V, with corresponding fields of 1.66 to 1.94 MV/cm. These results highlight the potential of LPCVD-grown and etched beta-Ga2O3 devices for high-performance power electronic applications.