The electron-beam-induced current (EBIC) method was employed to investigate the electrical activity of dislocations in silicon carbide Schottky and diffused p–n diodes. Dislocations in Schottky diodes appear as dark spots with the EBIC current signal at the dislocations reduced with respect to the background. However, in p–n diodes, the same dislocations exhibited characteristic bright halos, with the EBIC current higher than that of the background. These bright halos were attributed to a nonuniform impurity distribution around dislocations caused by the high-temperature (∼2000 °C) diffusion process.
The electron-beam induced current (EBIC) method was employed to investigate the electrical activity of dislocations in silicon-carbide-diffused p-n diodes. It was observed that EBIC contrast depends on the type of defect (superscrew, screw, and edge dislocation). This dependence was attributed to spatial inhomogeneities in the electrical properties of the material around the dislocations due to different impurity-dislocation interactions during high-temperature (∼1900°C) diffusion. Chemical etching of the sample was used to define the nature of the defects observed by EBIC imaging. It was found that electrical breakdown of the diodes occurs at the location of superscrew dislocations.
Numerical simulations of the thermal stress distribution in a SiC boule 2” in diameter and 1” long grown by conventional PVT technique were performed based on the temperature field distribution in a resistively heated growth reactor that was simulated using the GAMBIT-2.0.4/FIDAP-8.6.2 software package. Analysis of the simulation results revealed the existence of a thermal stress, which was excessively nonuniform in distribution and whose magnitude exceeded the value of the critical resolved shear stress of 1.0 MPa by a factor of 2. The high stress initiated plastic deformation and the high temperature provoked the intense self-diffusion processes. The combination of these factors alters the mechanism of plastic deformation, significantly affecting the structural quality of the growing crystal. The influence of self-diffusion processes initiating the formation of interstitial atoms and vacancies; stacking fault formation as a result of the nonconservative motion of the basal plane dislocations; and micropipe formation from the dislocation groups piled up at silicon and carbon second phase inclusions are also discussed.
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