β-Ga2O3 Schottky barrier height improvement using Ar/O2 plasma and HF surface treatments

In this report, we show that Ar/O2 plasma exposure followed by HF treatment improves the Schottky barrier height (SBH) in β-Ga2O3 Schottky barrier diodes (SBDs) by nearly 0.3 eV, resulting in a breakdown voltage (VBR) gain of over 100 V on 2 × 1016 cm−3 doped substrates, without compromising the specific on-resistance. The SBH and VBR enhancement is observed on (2¯01) as well as (001) surfaces. Through extensive surface characterization, the Ar/O2 plasma exposure is shown to amorphize and increase surface oxygen vacancy concentration. HF treatment cleans the surface damage and passivates the surface through fluorine adsorption, leading to Fermi-level de-pinning and SBH improvement. Remarkably, however, the Ar/O2 plasma exposure enhances fluorine adsorption when compared to fluorine treatment alone, resulting in a more substantial improvement in SBH and VBR. Surface clean/treatment plays a critical and fundamental role in determining the quality of the metal/β-Ga2O3 interface. The improved surface treatment process demonstrated in this work can be easily integrated with various field termination methods that can help further improve the β-Ga2O3 SBD performance.