Point defects in semiconductors are highly mobile species. They easily diffuse and interact among them and with other intrinsic or extrinsic defects. As a result, defect population evolve by recombining complementary defects (self-interstitials and vacancies) or by aggregation of the same type of defects through Ostwald ripening mechanism leading to extended defects. They can also interact with extrinsic defects (dopants, gettering centers, etc) enhancing dopant diffusivity or being trapped.
Our work in this topic ranges from the analysis of the dynamics of point defects (migration paths and energies, accessible by classical molecular dynamics techniques) to the evolution of extended defects, including their influence on dopant diffusivity and dopant-defect clustering which immobilizes and electrically deactivates dopant atoms (accessible by kinetic Monte Carlo techniques which allow the simulation of device structures at a macroscopic scale).
Animation showing amorphization and recrystallization processes as obtained by atomistic kinetic Monte Carlo simulations. Ion implantation generates Si interstitials (I, blue spheres) and vacancies (V, red spheres). Amorphization is modeled by the accumulation of IV pairs (green spheres) during ion implantation creating a continuous amorphous layer. Subsequent anneals lead to IV pair annihilation, leaving the amorphous layer free of defects and a band of Si interstitial defects beyond the amorphous/crystalline interface (P. López et al., Materials Science and Engineering B 114-115, 82 (2004) - Atomistic modeling of defect evolution in Si for amorphizing and subamorphizing implants).
Evaluation of the atomic structure of relevant defects and complexes
Modeling of the relevant energies that govern the stability and diffusion of defects
Calculation of the electronic levels of defects to correlate with their macroscopic effects
Simulation of dynamics of defects based on fundamental properties