Effect of PKA energy and temperature on displacement damage in GaN and In0.25Ga0.75N

Abstract

Molecular Dynamics is used to simulate displacement damage in GaN and In0.25Ga0.75N materials. To investigate the effects of energy and temperature on defect evolution, the collision cascades are simulated under different PKA energies (2-10 keV) and temperatures (100-900 K). The impacts of energy and temperature on the number of defects are distinct. When PKA energy becomes higher, both the peak number (Np) and stable number (Ns) of Frenkel pairs increase. However, increasing the temperature raises Np but has little effect on Ns. With respect to the type of defects, it is observed that the number of Ga vacancies (VGa) is the largest both in GaN and In0.25Ga0.75N, which may be due to its low formation energy. It is also found that PKA energy affects the recombination rate (η) of different atom‑related defects in different ways. The higher PKA energy increases the η of Ga-related defects, while decreasing the η of N-related defects and In-related defects. It is widely known that high temperature normally promotes the annealing of defects. However, as the temperature rises, we observe that the η of Ga-related defects and In-related defects reduces in In0.25Ga0.75N. A possible reason is that the site-competition behavior between Ga atoms and In atoms creates antisites, which can be quantified by the temperature-dependent diffusion kinetics. We calculate the diffusion coefficients using the Arrhenius relationship, and the results show that D increases from 7.6×10−61 to 10−23 cm2/s when the temperature increases from 300 K to 900 K. The enhanced thermal energy promotes defect interactions and antisite formation, thereby hindering annealing and reducing the η of defects. Besides, the clusters produced during the collision cascade under high PKA energy are analyzed. The results show that the increasing temperature causes large clusters to decompose into small clusters or point defects, and vacancies are more likely to form large clusters than antisites.