Control and understanding of metal contacts to β-Ga₂O₃ single crystals: a review

Gallium oxide (Ga₂O₃) is a promising semiconductor for high power devices and solar blind ultraviolet photodetectors due to its large bandgap, a high breakdown field, and high thermal stability. Recently, a considerable achievement has been obtained for the growth of high-quality β-Ga₂O₃ and high performance β-Ga₂O₃ based devices. However, rapid advance in device performance can be limited by the critical issues of metal contacts to β-Ga₂O₃ such as barrier height, leakage current, ohmic contact, and surface, interfacial and deep states. This article aims to provide a review on the recent studies in the control and understanding of metal contacts to β-Ga₂O₃, particularly in terms of the barrier formation. This review suggests that understanding the current transport mechanisms of metal contacts to β-Ga₂O₃ more thoroughly is necessary to enhance the performance, stability and reliability of β-Ga₂O₃ based devices.