A novel structure of a high current gain 4H-SiC BJT with a buried layer in the base

In this paper we report on the effect of temperature and injection level on the effective lifetime of non-equilibrium charge carriers in p-base of 4H-SiC PiN diodes. Studies were carried out on 1kV drift step recovery diodes (DSRDs) with p+-p--n+. The lifetime of non-equilibrium charge carriers in 4H-SiC p+-p--n+ structures increases by an average of 6 times from 250ns to 1.4μs with the increase of the samples temperature from 300K to 673K. However, increase of the injection level in the drift region from 2.3·1016cm-3 to 5.9·1016cm-3 does not affect the lifetime indicating that Shockley-Read-Hall recombination processes are dominating.

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“…Following [6,7], the lifetime of the charge carriers can be described as a function of temperature and doping:…”

Section: Resultsmentioning

confidence: 99%

“…where τ 0 is the charge carrier lifetime in the low doped semiconductor, α = 1.72 [7], N is the doping level, N T is the concentration of recombination centers, γ = 0.3. For the simulated curve presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

Temperature Dependence of Minority Carrier Lifetime in Epitaxially Grown p+-p–-n+ 4H-SiC Drift Step Recovery Diodes

Afanasyev

Иванов

Ilyin

et al. 2015

MSF

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“…Therefore, a high β is required to reduce the working loss as well as simplify the base drive circuit topology [7]. One of the main challenges is increasing the low β in the design and manufacture of SiC BJTs [8][9][10][11][12][13]. Surface recombination in the SiC/SiO 2 interface has been found to limit the current gain of the 4H-SiC BJTs [14].…”

Section: Introductionmentioning

confidence: 99%

Silicon carbide bipolar junction transistor with novel emitter field plate design for high current gain and reliability

Zhang

Chen

Luo

et al. 2019

Semicond. Sci. Technol.

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A silicon carbide bipolar junction transistor with novel emitter field plate (EFP-BJT) design is proposed in this paper. The fabricated EFP-BJT features a metal plate of the extending emitter electrode with a 50-nanometer-thick oxide layer overlapped on the extrinsic base surface. The contrast of experimental results show that a 56% increase of maximum current gain is obtained by the EFP-BJT compared with a conventional SiC BJT (C-BJT), with the EFP-BJT's current gain of 43 measured at the collector current density (J C ) of 716 A cm −2 corresponding to a specific on-state resistance (R SP_ON ) of 5.4 mΩ•cm 2 and open-base breakdown voltage (BV CEO ) of 1.5 kV. The novel EFP-BJTs are entirely compatible with the process and design considerations of the conventional ones. The in-depth mechanism comparisons between the proposed EFP-BJT and C-BJT are studied by the simulation tool TCAD Silvaco. The surface recombination effect of EFP-BJT is greatly reduced by the modulation of the emitter field plate. Additionally, due to the surface recombination suppression of the novel structure, EFP-BJTs have effectively enhanced reliability. Compared with C-BJTs, there is no significant degradation of the collector current for the fabricated EFP-BJTs under the forward current stress test.

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“…To reduce the surface recombination between SiC and SiO 2 along the emitter‐base sidewall, a suppressed surface recombination BJT structure [2] and a deep‐level‐reduction process [3] were proposed with special fabrication procedures. Also, the double‐base structure [4] and a single base with a buried layer [5] which could accelerate the electron transport in the base region were verified by experiment and simulation.…”

Section: Introductionmentioning

confidence: 99%

4H‐SiC work‐function‐dependent bipolar transistor with ultra‐high current gain

et al. 2014

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A new structure of a 4H-SiC bipolar transistor with ultra-high current gain is proposed and analysed by simulation. A p-type Schottky contact serving as the conventional emitter region is introduced. By proper choice of the metal work-function, the injection efficiency of the minority carrier (electron) is promoted and may be close to unity. Therefore high current gain is realised due to the high electron current density injected from the p-type Schottky contact. The simulation results show that the current gain varies with the metal work-function and could reach ∼1000, which is attractive for the base-drive circuit. Moreover, the new structure simplifies the etching process compared with the conventional bipolar junction transistor.Introduction: In past decades, bipolar junction transistors (BJTs) based on 4H-SiC have developed rapidly, owing to the superior properties of silicon carbide for high-power and high-temperature applications. As a current-driven switching and amplifying device, it is important to improve the current gain of BJTs for reducing the power losses in the drive circuit. Reducing the base thickness is a direct way, but the blocking characteristic will be significantly degraded [1]. To reduce the surface recombination between SiC and SiO 2 along the emitter-base sidewall, a suppressed surface recombination BJT structure [2] and a deep-level-reduction process [3] were proposed with special fabrication procedures. Also, the double-base structure [4] and a single base with a buried layer [5] which could accelerate the electron transport in the base region were verified by experiment and simulation.In the early years, a Schottky heterojunction bipolar transistor was proposed and demonstrated [6]. The current gain has a significant improvement, owing to the high injection efficiency of minority carriers in the Schottky heterojunction barrier emitter. It is worth noting that the high minority-to-majority carrier ratio has been demonstrated in the silicon tunnel transistor [7]. Furthermore, using this injection theory, silicon heterojunction emitter transistors with a current gain over 25 000 have been fabricated [8], and some new structures with a excellent performance have also been proposed [9,10]. In this Letter, we report a 4H-SiC work-function-dependent (WFD) bipolar transistor that replaces the conventional emitter region with the selected p-type Schottky contact. Using the theory of minority carrier injection in the Schottky contact, a large injection ratio of the minority-carrier (electron)-to-majority-carrier (hole) could be obtained due to the suppression of the majority carrier current by the large barrier height at the metal-SiC interface. Thus, the current gain is improved. Furthermore, the blocking characteristic could be maintained by the design of a floating-plate at the Schottky metal periphery.

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A novel structure of a high current gain 4H-SiC BJT with a buried layer in the base

Cited by 7 publications

References 17 publications

Temperature Dependence of Minority Carrier Lifetime in Epitaxially Grown p<sup>+</sup>-p<sup>–</sup>-n<sup>+</sup> 4H-SiC Drift Step Recovery Diodes

Temperature Dependence of Minority Carrier Lifetime in Epitaxially Grown p<sup>+</sup>-p<sup>–</sup>-n<sup>+</sup> 4H-SiC Drift Step Recovery Diodes

Silicon carbide bipolar junction transistor with novel emitter field plate design for high current gain and reliability

4H‐SiC work‐function‐dependent bipolar transistor with ultra‐high current gain

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