Using ground state and excited state density functional theory to decipher 3ddopant defects in GaN

Area of Science:

• Computational materials science
• Solid-state physics
• Defect physics

Background:

• Gallium nitride (GaN) is a key material for electronic and optoelectronic devices.
• Understanding 3d transition metal defects in GaN is crucial for device performance and novel applications.
• Existing interpretations of 3d defect electronic structures in GaN require reevaluation.

Purpose of the Study:

• To decipher the electronic structure of Mn and other 3d defects in GaN using advanced DFT methods.
• To reassign and reinterpret existing experimental data on 3d defects in GaN.
• To identify the specific defect responsible for the 1.19 eV photoluminescence in n-type GaN.

Main Methods:

• Ground state density functional theory (DFT) calculations.
• Occupation-constrained DFT (occ-DFT) for self-consistent excited state calculations.
• Validation against experimental defect levels and photoluminescence data.

Main Results:

• The electronic structure of Mn dopants and other 3d defects in GaN across the band gap were determined.
• Mn$_{Ga}$ defects exhibit stable charge states from (1-) in n-type GaN to (2+) in p-type GaN.
• The Mn(2+) defect has a $d^2$ spin triplet ground state and a singlet excited state, isoelectronic with the 1.19 eV photoluminescence defect.
• The 1.19 eV defect in n-type GaN is identified as V(0), not Cr(1+) as previously assumed.
• The DFT analysis demonstrated a capability for chemically fingerprinting defects.

Conclusions:

• The study mandates a reinterpretation of 3d defect data in GaN.
• The Mn(2+) defect is a viable candidate for quantum applications.
• The V(0) defect is responsible for the 1.19 eV photoluminescence in GaN.
• Combined ground-state and excited-state DFT analysis provides a powerful tool for defect characterization.