Deep chalcogen donors and electron localization in aluminum nitride

Area of Science:

• Materials Science
• Solid State Physics
• Computational Chemistry

Background:

• Aluminum nitride (AlN) is a wide-bandgap semiconductor with potential applications in electronics.
• Understanding dopant behavior is crucial for controlling AlN's electrical properties.
• Previous studies have explored various dopants, but deep donor states in AlN require further investigation.

Purpose of the Study:

• To investigate the electronic properties of chalcogen donors (S, Se, Te) in aluminum nitride (AlN).
• To determine if these chalcogen donors behave as shallow or deep dopants.
• To elucidate the origin of experimentally observed activation energies in doped AlN.

Main Methods:

• Hybrid density functional theory (DFT) calculations were employed.
• The electronic structure and charge states of S, Se, and Te in AlN were simulated.
• The formation and stability of electron polarons bound to dopants were analyzed.

Main Results:

• Chalcogen donors (S, Se, Te) in AlN form deep donor states, with levels 0.45 eV or more below the conduction band edge.
• This deep donor behavior is distinct from the DX center phenomenon observed in other dopants.
• Metastable small electron polarons are predicted to form when bound to these chalcogen dopants and Si.
• Calculated activation energies for polaron formation align with experimental observations (0.2–0.3 eV).

Conclusions:

• Sulfur, selenium, and tellurium are not shallow donors in aluminum nitride.
• The deep donor states and associated electron polarons explain the experimentally observed dopant activation energies.
• These findings provide critical insights for the design and fabrication of AlN-based electronic devices.