Ionization potentials of semiconductors from first-principles.

Area of Science:

• Solid-state physics
• Materials science
• Computational chemistry

Background:

• Ionization potential (IP) is critical for absolute band edge alignment with vacuum.
• Accurate theoretical determination of IPs is less developed than for band gaps.
• Semiconductor surface and interface properties heavily depend on band alignment.

Purpose of the Study:

• To evaluate state-of-the-art first-principles methods for semiconductor ionization potentials.
• To compare Kohn-Sham density functional theory (LDA/GGA) with many-body perturbation theory (GW approximation).
• To critically assess two GW correction schemes: Valence Band Maximum (VBM) and Band Gap Center (BGC).

Main Methods:

• First-principles calculations using Kohn-Sham density functional theory (LDA/GGA).
• Application of many-body perturbation theory within the GW approximation for quasi-particle corrections.
• Comparative analysis of the VBM and BGC GW correction schemes.

Main Results:

• LDA/GGA methods generally underestimate semiconductor ionization potentials.
• GW approximation significantly improves agreement between theoretical and experimental IPs.
• The VBM scheme demonstrates superior theoretical foundation and practical agreement compared to the BGC scheme.
• For materials with shallow semicore states, GW still shows discrepancies, suggesting limitations.

Conclusions:

• GW approximation, particularly the VBM scheme, is a reliable approach for calculating semiconductor ionization potentials.
• Standard LDA/GGA methods are insufficient for accurate IP determination.
• Further theoretical advancements beyond standard GW are needed for specific semiconductor classes (e.g., those with shallow semicore states).