A Low-Temperature Molten Alkali Etching Method for Rapid Defect Characterization in β-Ga2O3

Abstract β-Ga2O3 is a promising semiconductor material for next-generation high-power and high-efficiency electronics and photonics. To evaluate crystal quality, defect-selective etching provides a simple and effective route to visualize crystal defects. Common β-Ga2O3 etchants such as phosphoric acid, alkaline solutions, and NaOH–KOH molten eutectics are limited by high temperatures, lengthy procedures and poor stability. In this work, a low-temperature molten alkali etching method based on the KOH–KOH·H2O system is developed, which enables defect-selective etching across various β-Ga2O3 crystallographic planes such as (100), (010), (001) and (2 ̅01). Clear and well-defined etch pits can be observed via optical microscopy after 5–30 min of etching at 130 °C. Furthermore, systematic Focused Ion Beam and Transmission Electron Microscope characterizations confirm these etch pits originate from dislocations or voids. This work develops a novel and efficient technique for β-Ga2O3 defect characterization, providing solid support for crystal growth optimization, device failure analysis and the fabrication of high-performance β-Ga2O3-based devices.