Ultra-wide bandgap beta-gallium oxide (β-Ga2O3) has been attracting considerable attention as a promising semiconductor material for next-generation power electronics. It possesses excellent material properties such as a wide bandgap of 4.6-4.9 eV, a high breakdown electric field of 8 MV/cm, and exceptional Baliga's figure of merit (BFOM), along with superior chemical and thermal stability. These features suggest its great potential for future applications in power and optoelectronic devices. However, the critical issue of contacts between metal and Ga2O3 limits the performance of β-Ga2O3 devices. In this work, we have reviewed the advances on contacts of β-Ga2O3 MOSFETs. For improving contact properties, four main approaches are summarized and analyzed in details, including pre-treatment, post-treatment, multilayer metal electrode, and introducing an interlayer. By comparison, the latter two methods are being studied intensively and more favorable than the pre-treatment which would inevitably generate uncontrollable damages. Finally, conclusions and future perspectives for improving Ohmic contacts further are presented.
Keywords: Contacts; Intermediate semiconductor layer; Metal stacks; β-Ga2O3.