Dry etch damage anisotropy and damage mitigation using hot H3PO4 in (001) β-Ga2O3 Schottky diodes

β-Ga2O3 is a promising ultra-wide bandgap semiconductor for power devices. Here, we report on the fabrication of Schottky barrier diodes on (001) β-Ga2O3 to investigate both dry etch damage anisotropy and damage mitigation using H3PO4. Fabricated diode structures include planar diodes with Schottky contacts on etched and unetched surfaces, circular mesa diodes, and fin diodes whose long axis was aligned to either the [100] or [010] direction and whose short axis was divided between 1 and 9 fins. Evidence of dry etch damage in mesa and planar diodes on etched surfaces included increased effective Schottky barrier heights (SBHs) and ideality factors relative to planar diodes on unetched surfaces. [010]-aligned fin devices were resilient to dry etch damage, as their characteristics did not degrade as fin widths decreased to 5 μm. Conversely, the [100]-aligned fin devices, including those with 45 μm fin widths, exhibited larger effective SBHs, larger ideality factors, reduced capacitances, and reduced current densities relative to [010]-aligned devices. Planar diodes on etched surfaces recovered after a 15-min H3PO4 etch at 140 °C, while [100]-aligned fin diodes and mesa diodes did not fully recover after a 2-h etch. We speculate that ion channeling and defect diffusion cause the damage anisotropy. Dry-etch-damage-free fin diodes with alignment-independent characteristics were also demonstrated using an H3PO4 etch without an ICP etch. The work demonstrates the etch damage resilience of [010]-aligned devices and that the device structure determines whether H3PO4 etching is an effective tool for dry etch damage mitigation, elimination, or avoidance in (001) β-Ga2O3.