First-Principles insights into group-V impurities and their impact on germanium detector performance.

Area of Science:

• Materials Science
• Nuclear Physics
• Computational Physics

Background:

• High-purity germanium (HPGe) detectors are crucial for nuclear physics research, offering excellent energy resolution and sensitivity.
• Defects and impurities in HPGe crystals cause charge trapping, degrading detector performance and energy resolution.

Purpose of the Study:

• To investigate the energetics of point defects in germanium (Ge) using density functional theory.
• To understand the impact of group-V impurities and their complexes with vacancies on charge trapping in HPGe detectors.

Main Methods:

• Density functional theory (DFT) calculations with hybrid functionals were employed.
• The study focused on the formation energies and electronic properties of point defects in Ge.

Main Results:

• Group-V impurities (P, As, Sb) are more likely to form in Ge than vacancies or interstitials.
• Nitrogen (N) creates deep trap states, while P, As, and Sb form shallow traps near the conduction band edge.
• Group-V defects can form complexes with Ge vacancies, creating deep traps that contribute to charge trapping.

Conclusions:

• Both Ge vacancies and vacancy-impurity complexes are significant contributors to charge trapping in HPGe detectors.
• Understanding these defects is crucial for improving the performance and reliability of HPGe detectors for sensitive nuclear measurements.