Direct observation and three dimensional structural analysis for threading mixed dislocation inducing current leakage in 4H–SiC IGBT

Konishi, Kazuya; Nakamura, Yu; Nagae, Akemi; Kawabata, Naoyuki; Tanaka, Takanori; Tomita, Naohide; Watanabe, Hiroshi; Tomohisa, Shingo; Miura, Naruhisa

doi:10.7567/1347-4065/ab5ee8

Cited by 9 publications

(8 citation statements)

References 33 publications

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“…23−25 More significantly, both synchrotron X-ray-topography (XRT) and transmission-electron-microscopy (TEM) investigations have verified that TMDs are the dominant configurations of TSD/ TMDs in 4H-SiC. 26,27 However, the morphology of the etch pits of TMDs is still ambiguous, which leads to difficulty in the statistics of the density of TMDs in 4H-SiC. In addition, it has been found that electrons tend to accumulate at TSDs, 28 while the electronic properties of TEDs are still not clear.…”

Section: Introductionmentioning

confidence: 99%

“…Molten-alkali etching is usually adopted to reveal dislocations in 4H-SiC, which removes strained atoms surrounding TDs and forms etch pits at the surface of 4H-SiC. , Researchers have established an empirical approach to distinguish TSDs from TEDs by assuming that the average size of the etch pits for TSDs is 1.6–2.1 times larger than that of the etch pits for TEDs . However, the shapes, densities, and sizes of molten-alkali etched pits significantly vary with the alkali species, etching duration, and doping concentration of 4H-SiC, makes it difficult to discriminate. − More significantly, both synchrotron X-ray-topography (XRT) and transmission-electron-microscopy (TEM) investigations have verified that TMDs are the dominant configurations of TSD/TMDs in 4H-SiC. , However, the morphology of the etch pits of TMDs is still ambiguous, which leads to difficulty in the statistics of the density of TMDs in 4H-SiC. In addition, it has been found that electrons tend to accumulate at TSDs, while the electronic properties of TEDs are still not clear.…”

Section: Introductionmentioning

confidence: 99%

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Electronic and Optical Properties of Threading Dislocations in n-Type 4H-SiC

Luo

Yang

et al. 2022

ACS Appl. Electron. Mater.

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Despite the decades of development of the single-crystal growth and homoepitaxy of 4H silicon carbide (4H-SiC), high-density threading dislocations (TDs) still remain in 4H-SiC. In this work, we show that the diameters, depths, and inclination angles of molten-alkali etched pits can be employed to discriminate threading edge dislocations (TEDs), threading screw dislocations (TSDs), and threading mixed dislocations (TMDs) in 4H-SiC. The formation of etch pits of TEDs, TSDs, and TMDs during molten-alkali etching is found to be assisted by the dislocation line, dislocation step, and successively dislocation line and step, respectively. By inspecting the surface potentials of n-type 4H-SiC with Kelvin probe force microscopy (KPFM), we show that both TSDs and TEDs behave as donors in n-type 4H-SiC, which gives rise to charge depletion at TDs in n-type 4H-SiC. TDs are found to participate in the broad band D1 luminescence of 4H-SiC, as evidenced by the fact that the microphotoluminescence (micro-PL) intensities at the centers of TDs are stronger than those in dislocation-free regions of 4H-SiC. Understandings gained in this work may help the optimization of n-type 4H-SiC by manipulating the electronic and optical properties of TDs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electronic and Optical Properties of Threading Dislocations in n-Type 4H-SiC

Luo

Yang

et al. 2022

ACS Appl. Electron. Mater.

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“…Figure 1A displays the OM image of the molten-KOH etched 4H-SiC epitaxial layer. The larger hexagonal pits, the smaller hexagonal pits, and the sea-shell pits correspond to the etch pits of TSDs/TMDs, TEDs, and BPDs, respectively (Konishi et al, 2019;Katsuno et al, 2011;Dong et al, 2013). By the statics of wafer-scale etch-pit density of different dislocations, the average dislocation densities of TSDs/TMDs, TEDs and BPDs are 3,770/cm 2 , 2,352/cm 2 , and 18/cm 2 , respectively.…”

Section: Resultsmentioning

confidence: 97%

“…It has been found that all the dislocations increase the leakage current of 4H-SiC power devices, and the effect of TSDs is more prominent than those of TEDs (Wahab et al, 2000;Berechman et al, 2010). As evidenced by synchrotron X-ray-topography (XRT) and transmission-electron-microscopy (TEM) investigations, TMDs dominate the configurations of the TSD/TMDs in 4H-SiC, while the effect of TMDs on the leakage current of 4H-SiC based high-power devices is still ambiguous (Onda et al, 2013;Konishi et al, 2019;Shinagawa et al, 2020). Meanwhile, the leakage current originating from BPDs was found in 4H-SiC p-n diodes and bipolar junction transistors (BJTs) (Muzykov et al, 2009;Skowronski and Ha, 2006;Ota et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Dislocation-related leakage-current paths of 4H silicon carbide

et al. 2023

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Improving the quality of 4H silicon carbide (4H-SiC) epitaxial layers to reduce the leakage current of 4H-SiC based high-power devices is a long-standing issue in the development of 4H-SiC homoepitaxy. In this work, we compare the effect of different type of dislocations, and discriminate the effect of dislocation lines and dislocation-related pits on the leakage current of 4H-SiC by combining molten-KOH etching and the tunneling atomic force microscopy (TUNA) measurements. It is found that both the dislocation lines of threading dislocations (TDs) and the TD-related pits increase the reverse leakage current of 4H-SiC. The dislocation lines of TDs exert more significant effect on the reverse leakage current of 4H-SiC, which gives rise to the nonuniform distribution of reverse leakage current throughout the TD-related pits. Due to the different Burgers vectors of TDs, the effect of TDs on the reverse leakage current of 4H-SiC increases in the order to threading edge dislocation (TED), threading screw dislocation (TSD) and threading mixed dislocation (TMD). Basal plane dislocations (BPDs) are also found to slightly increase the reverse leakage current, with the leakage current mainly concentrated at the core of the BPD. Compared to the effect of TDs, the effect of BPDs on the reverse leakage current of 4H-SiC is negligible. Our work indicates that reducing the density of TDs, especially TMDs and TSDs, is key to improve the quality of 4H-SiC epitaxial layers and reduce the reverse leakage current of 4H-SiC based high -power devices.

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“…Because as mentioned above, the WBV method is weighted toward dislocation lines at high angles to the analyzed surface. We should note that boundaries comprised of mixed edge and screw dislocations are theoretically possible (Foreman, 1955; Peach & Koehler, 1950; Weertman, 1965), but have been seldom observed (De Kloe, 2001; Konishi et al., 2020). Furthermore, although most intragranular boundaries in our samples appear to be comprised of edge dislocations, boundaries containing screw dislocations may also be present.…”

Section: Discussionmentioning

confidence: 98%

Using Misorientation and Weighted Burgers Vector Statistics to Understand Intragranular Boundary Development and Grain Boundary Formation at High Temperatures

et al. 2022

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During plastic deformation, strain weakening can be achieved, in part, via strain energy reduction associated with intragranular boundary development and grain boundary formation. Grain boundaries (in 2D) are segments between triple junctions, that connect to encircle grains; every boundary segment in the encircling loop has a high (>10°) misorientation angle. Intragranular boundaries terminate within grains or dissect grains, usually containing boundary segments with a low (<10°) misorientation angle. We analyze electron backscatter diffraction (EBSD) data from ice deformed at −30°C (Th≈ ${T}_{h}\approx $ 0.9). Misorientation and weighted Burgers vector (WBV) statistics are calculated along planar intragranular boundaries. Misorientation angles change markedly along each intragranular boundary, linking low‐ (<10°) and high‐angle (10–38°) segments that exhibit distinct misorientation axes and WBV directions. We suggest that these boundaries might be produced by the growth and intersection of individual intragranular boundary segments comprising dislocations with distinct slip systems. There is a fundamental difference between misorientation axis distributions of intragranular boundaries (misorientation axes mostly confined to ice basal plane) and grain boundaries (no preferred misorientation axis). These observations suggest during progressive subgrain rotation, intragranular boundaries remain crystallographically controlled up to large misorientation angles (>>10°). In contrast, the apparent lack of crystallographic control for grain boundaries suggests misorientation axes become randomized, likely due to the activation of additional mechanisms (such as grain boundary sliding) after grain boundary formation, linking boundary segments to encircle a grain. Our findings on ice intragranular boundary development and grain boundary formation may apply more broadly to other rock‐forming minerals (e.g., olivine, quartz).

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Direct observation and three dimensional structural analysis for threading mixed dislocation inducing current leakage in 4H–SiC IGBT

Cited by 9 publications

References 33 publications

Electronic and Optical Properties of Threading Dislocations in n-Type 4H-SiC

Electronic and Optical Properties of Threading Dislocations in n-Type 4H-SiC

Dislocation-related leakage-current paths of 4H silicon carbide

Using Misorientation and Weighted Burgers Vector Statistics to Understand Intragranular Boundary Development and Grain Boundary Formation at High Temperatures

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