Analysis of anisotropic ionization coefficient in bulk 4H-SiC with full-band Monte Carlo simulation

Fujita, Ryusei; Konaga, K.; Ueoka, Yoshiki; Kamakura, Yoshinari; Mori, Nobuya; Kotani, Takao

doi:10.23919/sispad.2017.8085321

Cited by 5 publications

(5 citation statements)

References 15 publications

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“…A shrink in the minigaps positively impacts the acceleration of electrons under a high electric field, and therefore will compensate for the influence of enhanced phonon scattering at an elevated temperature. This may be a reason for the very small temperature dependence of the electron impact ionization coefficient along SiC〈0 0 0 1〉, but further theoretical [117,118] and experimental studies are required to elucidate the involved mechanism.…”

Section: Discussionmentioning

confidence: 99%

Carrier lifetime and breakdown phenomena in SiC power device material

Kimoto¹,

Niwa²,

Okuda³

et al. 2018

J. Phys. D: Appl. Phys.

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Recent progress and current understanding of carrier lifetimes and avalanche phenomena in silicon carbide (SiC) are reviewed. The acceptor level of carbon vacancy (VC), called the Z1/2 center, has been identified to be the primary carrier lifetime killer in SiC. The VC defects can be eliminated by the introduction of excess carbon atoms followed by carbon diffusion in the bulk region. The true bulk lifetime after VC elimination was estimated to be approximately 110 µs. The doping dependence of carrier lifetimes in n- and p-type SiC is also presented. The impact ionization coefficients of electrons and holes were extracted in the temperature range of 298 to 423 K. The intrinsic critical electric field strength of SiC〈0 0 0 1〉 was determined to be 2.0, 2.5, and 3.3 MV cm−1 for doping densities of 1 × 1015, 1 × 1016, and 1 × 1017 cm−3, respectively, at room temperature; it slightly increased at elevated temperature. The obtained set of impact ionization coefficients has enabled us to accurately predict the breakdown voltage of SiC devices, including its temperature dependence. Due to the unusually low impact ionization coefficient of electrons, the breakdown voltage of a SiC p+n junction is about 6%–9% higher than that of an n+p junction with a given doping density.

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Section: Discussionmentioning

confidence: 99%

Carrier lifetime and breakdown phenomena in SiC power device material

Kimoto¹,

Niwa²,

Okuda³

et al. 2018

J. Phys. D: Appl. Phys.

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“…The impact ionization coefficients in widebandgap semiconductors have been investigated both experimentally [9][10][11][12] and theoretically. [13][14][15][16][17][18][19] It has not yet been clarified, however, to what extent band structure parameters other than E g , such as the effective mass and Brillouin zone (BZ) width, affect impact ionization. For example, the electron impact ionization coefficients of 4H-SiC are known to be very anisotropic though E g is, of course, independent of the direction of the applied electric field.…”

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confidence: 99%

“…For example, the electron impact ionization coefficients of 4H-SiC are known to be very anisotropic though E g is, of course, independent of the direction of the applied electric field. 18,20) This suggests significant impacts of the band structure parameters other than E g . In this study, we theoretically investigate the dependence of impact ionization coefficients on such band structure parameters by a Monte-Carlo simulation assuming analytical and tunable band structures.…”

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confidence: 99%

“…Here, a = 1.11 × 10 13 s −1 and b = 3.38 are used, 25) which are fitted to a first-principles calculation result for electrons in 4H-SiC based on the GW approximation. 26) = ¢ = E E 3.26 eV g g is used except for the discussion of E g dependence, where E g is varied while ¢ = E 3.26 eV g is kept.…”

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confidence: 99%

“…The impact ionization coefficient is calculated from the number of impact ionization events per unit displacement along the x-direction (parallel to the electric field). 18) First, we compute the temperature dependence of the electron impact ionization coefficients α in systems with different BZ widths. Figure 1 shows the electric field dependence of α at temperatures of 100, 300, and 500 K. In case of p a = k 0.5 nm ,…”

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confidence: 99%

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Theoretical analysis of band structure effects on impact ionization coefficients in wide-bandgap semiconductors

Tanaka

Kimoto

Mori

2020

Appl. Phys. Express

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This study theoretically investigates the effects of band structure parameters, such as the bandgap, effective mass, and Brillouin zone (BZ) width, on impact ionization coefficients. A Monte-Carlo simulation considering analytical and tunable band structures reveals that the smaller BZ width significantly reduces impact ionization coefficients, and its impacts can outperform those of the bandgap. The smaller BZ width also leads to positive temperature dependence of impact ionization coefficients, which is discussed focusing on the occurrence of the Bloch oscillation. Our results show the importance of the BZ width in discussing the behavior of impact ionization coefficients.

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