Wafer-Scale Polarity Engineering of Nitrides Enabled High-Mobility Two-Dimensional Electron Gas and Defective Luminescence

Nitride materials, renowned for their unique polarity properties, underpin modern electronics and photonics. In particular, the polarity discontinuity is expected to form two-dimensional electron gases (2DEGs), which are highly desirable for many applications, such as high-electron-mobility transistors (HEMTs). However, traditional epitaxial growth methods face challenges in achieving controllable and high polarization difference 2DEG interfaces. Here, we report the wafer-scale bonded fabrication of a polarity inversion aluminum nitride (AlN) interface, achieving a high-quality 2DEG with the mobility of ∼1.7× 10 3 cm 2 V –1 s –1 and average sheet charge density of 3.3 × 10 13 cm –2 at room temperature. We find the evidence of oxygen at the interface, and the unique Al–O bonding structure at the polarity inversion interface is confirmed by atomic-scale electron microscopy and spectroscopy, combined with first-principles calculations, to account for the formation of 2DEG. Furthermore, distinct ultraviolet luminescence at ∼3.8 eV is observed, originating from the oxygen defects at the interface. These findings deepen our understanding of polarity inversion in nitrides and provide new strategies for designing advanced semiconductor devices via polarity engineering.