Wet etch, dry etch, and MacEtch of β-Ga₂O₃: A review of characteristics and mechanism

β-Ga₂O₃, a promising ultra-wide bandgap material for future high-power electronics and deep-ultraviolet optoelectronics applications, has drawn tremendous attention in recent years due to its wide bandgap of ~ 4.8 eV, high breakdown electric field, and availability of substrates. However, the reported etch behavior of β-Ga₂O₃ and the quality of etched surfaces, as well as the associated interface characteristics, could limit the performance of β-Ga₂O₃ devices. In this article, the etchings of β-Ga₂O₃, including regular wet etching, photoelectrochemical etching (PEC), reactive ion etching (RIE) and metal-assisted chemical etching (MacEtch), are reviewed. A comparison of the etch rate, orientation dependence, aspect ratio, etching mechanism, and surface quality for each of these etching methods is presented and the step-by-step reactions in PEC and MacEtch are proposed to elucidate the etch mechanism. The challenges for these etching techniques for β-Ga₂O₃ are discussed. Graphic abstract: [Figure not available: see fulltext.]