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Formation of interfacial dislocations (IDs) and dislocation half-loop arrays (HLAs) and their appearance in 4H-SiC epi-wafers are investigated by X-ray topography and KOH etching analysis. Synchrotron reflection X-ray topography demonstrates the ability to image IDs and HLAs simultaneously and reveal their densities as well as spatial distributions in the epi-wafers. The vertical location of IDs in the epi-wafer is also examined by this technique. The influence of wafer warp, in-situ H2 etching prior to epitaxial growth, substrate off-angle as well as the growth face (Si-face and C-face) on the densities and spatial distributions of IDs and HLAs are discussed.
Synchrotron x-ray topography with a high-resolution setup using 1128 reflection was carried out on 4H-SiC epilayers. Four different shapes of threading-edge dislocation according to Burgers vector direction were observed. The four types of threading-edge dislocation images were calculated by computer simulation, and the experimental results correlated well with the simulation results. The detailed topographic features generated by plural screw dislocations and basal plane dislocations were also investigated.
Silicon carbide (SiC) substrates and epilayers contain many crystal defects, such as micropipes, screw dislocations, threading edge dislocations (TEDs), basal plane dislocations (BPDs) and stacking faults. To investigate these defects, synchrotron radiation topography is frequently carried out. When the monochromatic synchrotron X-ray topography is taken by the grazing-incidence reflection geometry using 11-28 reflection, screw dislocations, TEDs and BPDs are simultaneously seen and shown as different topographic images . Many studies of dislocations were reported using 11-28 reflections in 4H-SiC [1,2]. Topographic images of the dislocations have been analyzed by the ray-tracing method of computer simulation . However, experimental images of dislocations were not fully matched to the fine structure of simulation images, because of a lack of resolution in recording media: conventional films and nuclear emulsion plates . This time, we report obtaining high-resolution topographic images using a new recording medium, and compare results between the experiment and the computer simulation. Synchrotron topography in 11-28 reflection was carried out at SPring8 applying holography films as high-resolution recording media. The TED images are distinguished as four types, which have ribbon-like features with different rotating angles, through the use of the films. The four different TED images agree well with the computer simulated images which have been reported by Vetter et.al. taking into account of the different Burgers vector directions . By comparing the three topographic images taken at g=-12-18, 11-28 and 2-1-18, we confirmed experimentally that the four types of TED images originated from the difference of Burgers vector directions. We also investigated high-resolution topographic images of elementary screw dislocations, micropipes, and BPDs in 4H-SiC epilayers. The experimental image of screw dislocation fairly matched with simulated image. The fine features in the experimental topographic images of micropipes and BPDs are also compared with the simulated images in detail.  T. Ohno, H. Yamaguchi, S. Kuroda, K. Kojima, T. Suzuki, K. Arai: J. cryst. Growth. Vol. 260 (2004) 209.  H. Tsuchida, T. Miyanagi, I. Kamata, T. Nakamura, R. Ishii, K. Nakayama and Y.Sugawara: Jpn. J. Appl. Phys. Vol. 25, (2005), L806-808.  W. Vetter, H. Tsuchida, I. Kamata, M. Dudley: J. Appl. Cryst. Vol. 38, (2005), 442-447.
The structure of thermal oxide film thinner than 2nm on a SiC surface was investigated using in-situ infrared reflection absorption spectroscopy (IRAS). In the case of oxide films on 6H-SiC(0001), the peak frequencies of the TO mode (≈1050 cm−1) of the Si-O-Si stretch vibration shifts toward lower wave number with decreasing oxide thickness in the range of 0.2nm to 2nm and shift toward a higher frequency as the growth temperature rises. The LO mode (≈1250 cm−1) of the Si-O-Si stretch vibration remains almost constant with the increase in oxide thickness from 0.2 nm to 2 nm. These results indicate that there is a considerable difference in the structure near the interface between a thermally grown oxide layer formed on SiC and one formed on Si.
Fabrication and evaluation of high voltage n-type 4H-SiC Schottky barrier diodes (SBDs) using 27μm thick epitaxial layers were presented. To achieve the ideal value of the breakdown voltage, various parameters of junction termination extension (JTE) were investigated. We concluded that the termination of triple rings with the concentrations of 6×1017, 3×1017, 1.5×1017cm−1 outwardly was best with the simulations. The SBDs with this termination showed the blocking voltage up to 3.4kV, which is almost the ideal value. We also investigated the distribution of leakage currents at -600V in SBDs with various diameters up to 4mm. High yield was obtained in the SBDs with the diameters below 2mm. The SBDs with high leakage currents showed the excess currents in the low forward voltage region and lots of bright spots could be observed by optical beam induced current analysis.
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