Gallium nitride (GaN) is a wide bandgap semiconductor which has rapidly transformed the world by enabling micro LEDs and RF devices such as the high electron mobility transistor (HEMT). GaN has the great advantage in the application of high temperature and high-frequency power electronic devices owing to its unique properties, such as wide bandgap, high electron saturation velocity, high breakdown field and high electron conductivity of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructure.