34. Field-Effect Transistors 4

β-Ga₂O₃-based field-effect transistor (FET) is regarded as a promising candidate for the next-generation power electronics due to its ultrawide bandgap of 4.5–4.8 eV, estimated critical field of 8 MV/cm and decent intrinsic electron mobility limit of 250 cm²/Vs, yielding a high BFOM of more than 3000, which is several times higher than GaN and SiC. Meanwhile, β-Ga₂O₃ crystal also possesses a unique property that it has a large lattice constant of 12.23 Å along [100] direction, which allows a facile cleavage into thin belts or nano-membranes. Therefore, by transferring β-Ga₂O₃ nano-membrane from its bulk substrate to a foreign substrate, we can fabricate β-Ga₂O₃ on insulator FETs and then explore material and device potentials before β-Ga₂O₃ epitaxy technology becomes mature and the cost of the epi-wafers reduces significantly. In this chapter, we will focus on the nano-membrane-based FETs and their electrical interfaces, demonstrating record high drain current density of the devices, minimize the self-heating effect by the integration of nano-membrane on high thermal conductivity substrates and expand research direction toward a low-power and wide bandgap logic application.