The elucidation of high-field properties is particularly crucial for the device applications of wide-bandgap semiconductors. Understanding material properties and physical phenomena specific to high electric fields, such as carrier impact ionization, avalanche multiplication, tunneling phenomena, and saturation/deterioration of drift velocity, is essential for unraveling high-field physics directly influencing device characteristics.

Scandium aluminum nitride (ScAlN) possesses strong piezoelectricity, and it has been practically implemented as a thin-film acoustic wave filter, finding applications in devices such as smartphones. Furthermore, ScAlN serves as a ferroelectric material, exhibiting polarization inversion under applied electric fields. By integrating ScAlN with gallium nitride (GaN), it is hypothesized that two-dimensional electron polarization induced at the heterojunction interface can be enhanced and manipulated, leading to increased electron mobility and switching capabilities. Through crystal growth, fundamental material property assessments, and transistor prototyping, we are conducting foundational research for next-generation high-frequency communication applications.