Computer Simulation of Displacement Damage in Silicon Carbide
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Computer Simulation of Displacement Damage in Silicon Carbide R. Devanathan, F. Gao, and W. J. Weber Fundamental Science Directorate, Pacific Northwest National Laboratory, MS K8-93, Richland, WA 99352, U.S.A. ABSTRACT We have performed molecular dynamics simulation of displacement events on silicon and carbon sublattices in silicon carbide for displacement doses ranging from 0.005 to 0.5 displacements per atom. Our results indicate that the displacement threshold energy is about 21 eV for C and 35 eV for Si, and amorphization can occur by accumulation of displacement damage regardless of whether Si or C is displaced. In addition, we have simulated defect production in high-energy cascades as a function of the primary knock-on atom energy and observed features that are different from the case of damage accumulation in Si. These systematic studies shed light on the phenomenon of non-ionizing energy loss that is relevant to understanding space radiation effects in semiconductor devices.
INTRODUCTION Silicon carbide (SiC) is a wide band gap semiconductor that is chemically inert, and it has better thermal conductivity and a higher breakdown field compared to silicon [1]. SiC-based electronics can operate at temperatures as high as 850 K, which is well in excess of the operating temperature limit of Si-based electronics. In addition, SiC devices are radiation resistant and well suited for high power operation. The use of SiC devices and sensors greatly reduces the need for radiation shielding and cooling in spacecraft applications, leading to considerable weight savings [2]. SiC devices are well suited for the extreme environments (high temperature and high radiation) encountered by spacecraft during exploration of the solar system. In addition, SiC sensors can be used for direct process monitoring at extreme temperatures encountered in launch vehicles and high radiation conditions in nuclear reactors [3]. In order to advance SiC technology for spacecraft applications, a fundamental understanding of point defects, defect clusters, and line defects is needed. Irradiation by energetic particles, such as protons and electrons, can result in electron-hole pair production by ionization and production of vacancies, interstitials and anti-site defects by atomic displacement. The anti-site defect is a component of radiation damage in compound semiconductors that is not present in elemental semiconductors such as Si. These defects can degrade the electrical as well as physical properties of the material. The small distance and time scales associated with the displacement process preclude direct experimental observation, and necessitate the use of atomistic simulations to gain insights into the fundamentals of defect production by energetic particle irradiation. In an effort to understand the atomic-level details of the displacement process, we have simulated displacement damage accumulation on Si and C sublattices in SiC using molecular dynamics simulations. In the present report, we discuss the energy required to disp
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