Ap-type dopable ultrawide-bandgap oxide.

Area of Science:

• Materials Science
• Solid-State Physics
• Semiconductor Research

Background:

• Ultrawide-bandgap (UWBG) semiconductors typically exhibit unipolar doping, limiting their application potential.
• Achieving p-type conductivity in UWBG oxides is challenging due to the formation of self-trapped holes (small polarons).
• Rutile germanium oxide (r-GeO2) was recently proposed as a potential material to overcome this limitation, but with high acceptor ionization energies.

Purpose of the Study:

• To investigate the potential of rutile silicon dioxide (r-SiO2) for p-type conductivity.
• To compare the properties of r-SiO2 with other rutile oxides (TiO2, SnO2, GeO2) regarding hole trapping and acceptor ionization.
• To assess the viability of r-SiO2 as a promising UWBG material for efficient p-type doping.

Main Methods:

• Utilized hybrid density functional calculations to study the electronic properties of various rutile oxides.
• Analyzed hole trapping mechanisms and acceptor ionization energies in acceptor-doped rutile structures.
• Calculated impurity formation energies to assess compensation effects by native defects like oxygen vacancies.

Main Results:

• Rutile titanium dioxide (TiO2) and tin dioxide (SnO2) exhibit strong hole trapping at acceptor impurities, consistent with prior research.
• Self-trapped holes are found to be unstable in rutile silicon dioxide (r-SiO2), which has a wide band gap of approximately 8.5 eV.
• r-SiO2 demonstrates the lowest Group-III acceptor ionization energies among the studied rutile oxides, comparable to gallium nitride (GaN).

Conclusions:

• Rutile silicon dioxide (r-SiO2) emerges as a promising candidate for achieving efficient p-type conductivity in ultrawide-bandgap oxides.
• The instability of self-trapped holes and low acceptor ionization energies in r-SiO2 make it a potential outlier among UWBG materials.
• Acceptor impurities in r-SiO2 have sufficiently low formation energies, suggesting minimal compensation by oxygen vacancies under oxygen-rich conditions.