Insight of displacement cascade evolution in gallium arsenide through molecular dynamics simulations

S Tian and CH He and H He and WL Liao and YR Bai and YH Li, COMPUTATIONAL MATERIALS SCIENCE, 202, 111016 (2022).

DOI: 10.1016/j.commatsci.2021.111016

Displacement damage induced by space radiation is still a considerable challenge of expanding application of GaAs-based devices (e.g. solar cell, et al.) in space missions. In the current work, molecular dynamics (MD) simulations are applied to investigate displacement cascades evolution in GaAs at room temperature. A set of displacement events initiated by different energies (up to 50 keV) of primary knock-on atom (PKA) were simulated. An improved Wigner-Seitz (W-S) cell method was developed by introducing a simple criterion for more accurate identification of interstitials and antisites. Based on the present defect analysis method, the generation, evolution and distribution of point defects were discussed at first. Then, the mechanisms of both vacancy and interstitial cluster evolutions along simulation time were presented. The results indicate that both Ga and As type defects play the same crucial role among interstitials, antisites and vacancies. As the energy of PKA increases, the start points of heat spike phase postpone slightly. Moreover, the non-linear increase of surviving defects accompanied with the rise of the energy of PKA is considered as contribution of directly amorphous pockets. During the stage I of cascade, as time progresses, different size clusters show up in succession from small size (i.e., between 2 and 5) to larger size. The medium and large vacancy clusters virtually only exist in the middle of cascades, and the majority of vacancies belong to the categorizes of single vacancy and small clusters, especially at the end of cascades. However, the medium and large interstitial clusters incline to hold up or grow continually at the MD time scale once they build up. Meanwhile, interstitials in larger clusters (30 similar to) account for more fraction as the energy of particles increases.

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