Insight into the High Hole Concentration of p-Type Ga₂O₃ via In Situ Nitrogen Doping

The unclear p-type conduction mechanism and lack of reliable p-type Ga₂O₃ severely hinder Ga₂O₃-based high-voltage electronics. Here, we demonstrate in situ nitrogen (N) doping via metal-organic chemical vapor deposition homoepitaxy using N₂O as oxygen source and acceptor dopant. Structural and compositional analyses confirm efficient N incorporation (favored by N-Ga bonding) compensating residual Si/H donors without compromising crystallinity. The Ga₂O₃:N epilayers achieve excellent p-type performance: 1.04 × 10¹⁸ cm^-3 hole concentration, 0.47 cm² V^-1 s^-1 mobility at room temperature, and 0.168 eV activation energy. A completely new insight into the p-type conduction mechanism in Ga₂O₃ is introduced, focusing on the crystallographic visualization of acceptors (N^2-) and holes (O^-), as well as the hole excitation process. It is suggested that careful suppression of the donor compensation effect and precise control of the N chemical potential, which leads to the fabrication of trace O^- species solid-dissolved within Ga₂O₃, are essential for achieving high-hole-concentration p-type conduction in oxides.