Multiscale Explanation of the Missing Gallium Vacancy in Gallium Arsenide

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Irradiation of gallium arsenide (GaAs) creates vacancies and interstitials.
• Experimental observation of the immobile gallium (Ga) vacancy has remained elusive despite decades of research.
• Static first-principles calculations predict Ga vacancies should be readily detectable.

Purpose of the Study:

• To resolve the conundrum of the missing Ga vacancy in irradiated GaAs.
• To investigate the role of short-time dynamical evolution of primary defects.
• To explain the discrepancy between theoretical predictions and experimental observations.

Main Methods:

• Utilized a dynamical multiscale atomistically informed device engineering (AIDE) method.
• Simulated the initial displacement damage and defect evolution.
• Analyzed the interaction between Ga vacancies and As interstitials.

Main Results:

• The Ga vacancy (3-/2-) defect level pins the Fermi level near midgap during initial damage.
• This pinning produces oppositely charged vacancies and interstitials.
• Fast arsenic (As) interstitials preferentially annihilate Ga vacancies due to Coulomb attraction, reducing their population below detection limits.

Conclusions:

• Short-time defect dynamics, specifically the annihilation of Ga vacancies by As interstitials, explains the missing Ga vacancy.
• The dynamical model resolves the experimental mystery and highlights the importance of multiscale approaches.
• This study reveals critical dynamical chemical behavior in short-time regimes, previously inaccessible experimentally.