Optimization ofp-type conductivity in lithium niobate by co-doping strategy

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Stable p-type conductivity in lithium niobate (LiNbO3) is essential for developing advanced optoelectronic devices.
• Previous attempts using mono-acceptor nitrogen (N) doping resulted in deep defect levels, hindering device performance.

Purpose of the Study:

• To identify an effective p-type dopant for LiNbO3 and develop a strategy to create shallow acceptor levels.
• To overcome the limitations of N-only doping by passivating the nitrogen dopant with magnesium (Mg).

Main Methods:

• First-principles calculations were employed to screen potential p-type dopants.
• A two-step co-doping process involving N and Mg was proposed and theoretically analyzed.
• Defect levels, transition energies, and formation energies were calculated using first-principles methods.

Main Results:

• Nitrogen (N) was identified as a promising p-type dopant, but mono-doping created deep levels (0.415 eV above VBM).
• Co-doping with N and Mg, followed by excess N doping, created shallow defect levels only 0.115 eV above the VBM.
• The co-doping strategy significantly reduced defect formation energy (by ~1.9 eV) and enhanced dopant solubility and stability.

Conclusions:

• The proposed donor and excess acceptor co-doping strategy effectively converts deep defect levels into shallow acceptor levels in p-type LiNbO3.
• This approach enhances local doping stability and reduces defect formation energy, paving the way for LiNbO3-based p-n junction and active optoelectronic devices.