Threshold displacement energies and displacement cascades in 4H-SiC: Molecular dynamic simulations

Weimin Li,Mianxin Song,Hui Guo,Shuqing Jiang,Lielin Wang,Faqin Dong,Jianli Shao,Liang Bian

doi:10.1063/1.5093576

Abstract

Molecular dynamic (MD) simulations were used to study threshold displacement energy (TDE) surface and Si displacement cascades in 4H-SiC system. To figure out the role of different Wyckoff sites in determining the TDE values, both Si and C atoms in 2a and 2b Wyckoff sites were separately considered as the primary knocked atoms (PKA). The initial kinetic energy was then distributed along 146 different crystallographic directions at 10 K. TDE surface appeared highly anisotropic for Si and C displacements along different crystallographic directions. The TDE was determined as 41 eV for Si and 16 eV for C. The average values of TDE over two Wyckoff sites were estimated to 66 eV for Si PKA and 24 eV for C PKA. The displacement cascades produced by Si recoils of energies spanning varied from 5 keV to 50 keV at 300 K. To count the number of point defects using Voronoi cell analysis method, the crystal structure of 4H–SiC was transformed from hexagonal to orthorhombic. It was found that the surviving defects at the end of cascades were dominated by C vacancies and interstitials due to low displacement energies of C atoms and greater number of C interstitials when compared to C vacancies.

Highlights

Silicon carbide (SiC) is an important semiconductor with wide application prospects in high temperature, frequency, and power microelectronic devices
Due to variations in atomic arrangements in different Wyckoff sites, the threshold displacement energy (TDE) in 2a Wyckoff site must be different from 2b Wyckoff site in the same crystallographic direction
TDE in 2a and 2b Wyckoff sites were computed for Si and C atoms

Summary

INTRODUCTION

Silicon carbide (SiC) is an important semiconductor with wide application prospects in high temperature, frequency, and power microelectronic devices. This is mainly due to its wide band gap, high breakdown voltage, and elevated saturation electron mobility.. During the process of energetic particles irradiation, SiC lattice produces large numbers of defects. These lead to degradation of its physical, chemical and mechanical properties, which, in turn, directly determine the feasibility and reliability of SiC in anti-irradiation fields. The TDE of each Wyckoff site along the same crystallographic direction should be different due to variations in atomic arrangements. The displacement cascades produced by Si-recoils at energies spanning from 5 to 50 keV were simulated at 300 K

SIMULATIONS

RESULTS AND DISCUSSION

CONCLUSIONS