Establishing Doping Limits for ZnGa₂O₄ for Ultrawide-Band-Gap Semiconductor Applications.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Zinc gallium oxide (ZnGa2O4) is an ultrawide-band-gap oxide with potential for transparent conductors and deep-ultraviolet (deep-UV) electronics.
• However, its transport properties and doping limitations are not well understood, hindering practical applications.

Purpose of the Study:

• To computationally investigate the intrinsic and extrinsic doping limits of ZnGa2O4.
• To understand the factors limiting electron mobility and achievable carrier concentrations.
• To evaluate the potential for both n-type and p-type conductivity in ZnGa2O4.

Main Methods:

• Hybrid density functional theory (DFT) calculations.
• Density functional perturbation theory (DFPT) for electron-phonon interactions.
• Advanced transport modeling.
• Defect and dopant formation energy calculations.

Main Results:

• ZnGa2O4 exhibits a dispersive conduction band with low effective mass, enabling high phonon-limited mobilities (approaching 500 cm2 V-1 s-1).
• Impurity scattering significantly limits mobility at relevant carrier concentrations.
• Electron-phonon coupling causes asymmetric band gap renormalization, crucial for reproducing intrinsic carrier concentrations (~9 × 10^19 cm-3).
• Ga/Zn antisites dominate defect behavior, leading to degenerate n-type conductivity.
• P-type conductivity is unlikely due to deep acceptor levels and polaron formation.
• Extrinsic doping offers limited potential for further carrier enhancement due to high formation energies or deep trap states.

Conclusions:

• This study establishes the fundamental doping limits of ZnGa2O4, driven by intrinsic defects and scattering mechanisms.
• While ZnGa2O4 shows promise as a deep-UV transparent conductor, optimization challenges remain.
• The findings provide crucial insights for designing and fabricating high-performance ZnGa2O4-based electronic devices.