Determination of the Core-structure of Shockley Partial Dislocations in 4H-SiC
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1069-D03-03
Determination of the Core-structure of Shockley Partial Dislocations in 4H-SiC Yi Chen1, Ning Zhang1, Xianrong Huang2, Joshua D Caldwell3, Kendrick X Liu3, Robert E Stahlbush3, and Michael Dudley1 1 Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY, 11794-2275 2 National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 119735000 3 Naval Research Laboratory, Washington, DC, 20375-5320 ABSTRACT Synchrotron x-ray topographs taken using basal plane reflections indicate that the electron-hole recombination activated Shockley partial dislocations in 4H silicon carbide bipolar devices appear as either white stripes with dark contrast bands at both edges or dark lines. In situ electroluminescence observations indicated that the mobile partial dislocations correspond to the white stripes in synchrotron x-ray topographs, while immobile partial dislocations correspond to the dark lines. Computer simulation based on ray-tracing principle indicates that the contrast variation of the partial dislocations in x-ray topography is determined by the position of the extra atomic half planes associated with the partial dislocations lying along their Peierls valley directions. The chemical structure of the Shockley partial dislocations can be subsequently determined unambiguously and non-destructively. INTRODUCTION Silicon carbide (SiC) has been more and more widely used in devices for high voltage and high temperature applications. However, the forward voltage drop under forward biasing in bipolar devices, due to the expansion of basal stacking faults (SFs) from the advancement of Shockley partial dislocations, degrades the SiC-based bipolar devices dramatically and eventually kills them. The advancement of Shockley partial dislocations is activated by the electron-hole recombination enhanced dislocation glide (REDG) process [1-4] and the driving force are still under discussion [5, 6, 7]. The properties of partial dislocations in semiconductors, not only their mobility but especially their possible energy states in the band gap, must depend on their structure configurations. For example, first-principles calculation indicates that the reconstructions along the dislocation lines can be electrically active by giving rise to energy states in the forbidden band gap [8]. Thus, it is of great importance to understand the chemical structures of partial dislocations so as to study their influence on energy states in the band gap. S. Ha and X. J. Ning have employed transmission electron microscopy to determine the core structure of partial dislocations in SiC [ 9 , 10 ]. The rigid sample preparation process in transmission electron microscopy makes it difficult and destructive to distinguish the chemical structure of the Shockley partial dislocations. We are introducing a simple, unambiguous and non-destructive way to determine the chemical structure of the Shockley partial dislocations.
EXPERIMENT The 4H-SiC substrates used in this study were commercially available wa
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