【Member Papers】Universal Role of Dopant-VGa Complexes Induced Carrier Suppression in Si/Ge/Sn/Zr-doped β-Ga₂O₃

      Researchers from the Wuhan University have published a dissertation titled " Universal Role of Dopant-V_Ga Complexes Induced Carrier Suppression in Si/Ge/Sn/Zr-doped β-Ga₂O₃ " in Applied Physics Lettes.

Background
      β-Ga₂O₃, with its ultra-wide bandgap (~4.9 eV) and high breakdown field, is regarded as a key material for high-power electronic devices. In this context, achieving efficient and stable n-type doping is fundamental for advancing the practical application of β-Ga₂O₃ in electronic devices. Dopants such as Si, Sn, Ge, and Zr can introduce shallow donor defects in β-Ga₂O₃, but their n-type doping efficiency is limited by the “self-compensation” effect, which makes it challenging to further increase the carrier concentration. Although previous studies have identified V_Ga (gallium vacancies) as a critical compensating defect, the systematic atomic-scale compensation mechanisms associated with these four major n-type dopants—including their formation origins and energy level positions—have not yet been fully understood.

Abstract

      The development of high-performance β-Ga₂O₃ electronics is critically hindered by the fundamental limitation of self-compensation in n-type doping, which severely suppresses free carrier concentrations. To explore the microscopic mechanism of this effect, we systematically investigate the four n-type dopants (Si, Sn, Ge, and Zr) in β-Ga₂O₃, combining first-principles calculations and experimental investigations. The calculation results show that the lower formation energies of Si_GaV_Ga and Sn_GaV_Ga complexes compared to Ge_GaV_Ga and Zr_GaV_Ga complexes lead to their higher concentrations and consequently stronger compensation in Si and Sn doping β-Ga₂O₃ under O-rich conditions. Oxygen annealing induces a severe compensation effect, as consistently validated by Hall effect and non-contact eddy current measurements. Beyond this universal mechanism, we further identify that the carrier compensation predominantly occurs near the surface, manifesting as a dramatic drop in near-surface carrier concentration and a sharp increase in contact resistivity in Sn-doped β-Ga₂O₃. Furthermore, photoluminescence spectra exhibit distinct green emission (∼2.5 eV), confirming the formation of the predicted deep-level defects Sn_GaV_Ga. This work reveals the microscopic compensation mechanism, providing vital theoretical and experimental insights for optimizing n-type β-Ga₂O₃ conductivity.

Conclusion

      This study combines theoretical calculations with experimental validation to investigate the self-compensation effect in n-type β-Ga₂O₃. Density functional theory (DFT) calculations indicate that stable X_GaV_Ga complexes (X = Si, Ge, Sn, Zr) act as the primary defect centers responsible for carrier compensation, severely limiting the n-type conductivity of the material. Among them, the formation of Si_GaV_Ga and Sn_GaV_Ga complexes is particularly pronounced. This theoretical prediction was experimentally confirmed in Sn-doped β-Ga₂O₃: after annealing in an oxygen atmosphere, the carrier concentration decreased from ~10¹⁸ cm⁻³ (room-temperature Hall measurement) to 10¹⁶ cm⁻³ (high-temperature Hall measurement above 600 K). Photoluminescence (PL) spectra exhibited characteristic emission peaks around 2.5 eV associated with deep-level defects, corresponding well to the Sn_GaV_Ga complexes formed during annealing, further supporting the proposed defect configuration. This work elucidates the atomic-scale physical origin of self-compensation across different doping systems, providing key theoretical and experimental guidance for optimizing β-Ga₂O₃ conductivity via annealing atmosphere control and defect suppression, and holds significant implications for advancing its application in high-performance power electronic devices.