This paper reviews the status quo of several GaN-based power devices. By using unique polarized heterostructure of GaN/AlGaN materials, NSJ (Natural Super Junction) diode was proposed to break through the trade-off between the blocking voltage and the on-resistance. Normally-off GaN-based device was realized by GIT (Gate Injection Transistor) structure, where p-type AlGaN hole-injector are provided as a gate reducing the on-resistance by conductivity modulation. Experimentally fabricated inverter system using GaN GIT achieved the world-highest conversion efficiency over 99.3%. Further, by combining the microwave performance and power handling capability of of GaN-based devices, we developed Drive-by-Microwave (DbM) technology as a DC-isolated gate driver for GaN power switch. This is a fusion of microwave and power devices for the first time using GaN-based materials.