# Electrical Characterization of HV (10 Kv) Power 4H-SiC Bipolar Junction Transistor

Pierre Brosselard, Brenda Fosso-Sob, Dominique Planson, Pascal Bevilacqua, Camille Sonneville, Mihai Lazar, Bertrand Vergne, Sigo Scharnholz, Hervé Morel

<figure><img src="image_1.png" /></figure>

To cite this version:

Pierre Brosselard, Brenda Fosso-Sob, Dominique Planson, Pascal Bevilacqua, Camille Sonneville, et al. Electrical Characterization of HV (10 Kv) Power 4H-SiC Bipolar Junction Transistor. Key Engineering Materials, 2025, 1021, pp.1-6. 10.4028/p-T0Vjdb. hal-05293324

HAL Id: hal-05293324

https://hal.science/hal-05293324v1

Submitted on 1 Oct 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Electrical Characterization of HV (10 kV) Power 4H-SiC Bipolar Junction Transistor

Pierre Brosselard<sup>1)</sup>, Brenda Fosso-Sob<sup>1)</sup>, Dominique Planson<sup>1)</sup>, Pascal Bevilacqua<sup>1)</sup>, Camille Sonneville<sup>1)</sup>, Mihai Lazar<sup>2)</sup>, Bertrand Vergne<sup>3)</sup>, Sigo Scharnholz<sup>3)</sup> and Hervé Morel<sup>1)</sup>

1) INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale Lyon, CNRS, Ampère, UMR-5005, F-69621, France

2) Light, Nanomaterials, Nanotechnologies, L2n, UMR CNRS7076, Université de Technologie de Troyes, 10004, Troyes, France

3) ISL, French-German Research Institute of Saint Louis, 5 rue Général Cassagnou, 68301 Saint Louis, France

**Keywords:** 4H-SiC, Bipolar Junction Transistor, Electrical Characterization, High Voltage

**Abstract:** In this paper, the static and dynamic characterization of a High Voltage (10kV) 4H-SiC Bipolar Junction Transistor (BJT) is presented. Using a high-voltage source in vacuum conditions, a breakdown voltage of 11 kV was measured. Results showed that both large and small BJTs exhibit similar on-state resistance per unit area and collector current density of 55 A.cm⁻². The current gain increases with a decrease in temperature, indicating reduced charge carrier recombination at lower thermal energies. Also, BJT have been characterized in switching mode at 1 kV. The study concludes that 4H-SiC BJT demonstrates promising electrical performance for high-efficiency applications in harsh environments.

## Introduction:

4H-SiC Bipolar Junction Transistors (BJTs) offer significant advantages for high-voltage and high-temperature applications due to their superior characteristics, including low on-state resistance and elevated breakdown voltage [1]-[2]. These devices are highly efficient in various sectors. However, their performance can be affected by temperature change. Therefore, it is very interesting to study its behavior in extreme conditions, especially in high-power applications [3]-[4]. After a short description of the BJT structure, electrical characterization in static mode for a temperature range from -50°C up to 150°C will be demonstrated. This work reports the switching characteristics of the BJT using a double source test bench which involves providing controlled input pulses to the base while monitoring the response at the collector.

## BJT's Structure

The BJTs were designed and fabricated on a 4H-SiC wafer with an epitayer of 120 µm thick and doping concentration of 8×10<sup>+14</sup> cm<sup>-3</sup>(Fig.1). Mesa with JTE (Junction Termination Extension) and JTE rings has been implemented for the edge termination. A 500 nm Si<sub>3</sub>N<sub>4</sub> layer has been deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition), yellow layer in Fig. 1 and also a thick polymide layer (brown layer in Fig. 1) is used for the device passivation. Three unique configurations of BJTs, each with varying finger length and active area, designed to enhance their electrical performance. The configurations include two distinct

<footnote n="1"><sup>1</sup>pierre.brosselard@insa-lyon.fr, <sup>1</sup>brenda.fosso-sob@insa-lyon.fr,</footnote>

<footnote n="1"><sup>1</sup>dominique.planson@insa-lyon.fr, <sup>1</sup>pascal.bevilacqua@insa-lyon.fr,</footnote>

<footnote n="1"><sup>1</sup>camille.sonneville@insa-lyon.fr, <sup>2</sup>mihai.lazar@utt.fr, <sup>3</sup>bertrand.bergne@isl.eu,</footnote>

<footnote n="3"><sup>3</sup>sigo.scharnholz@isl.eu, <sup>1</sup>herve.morel@insa-lyon.fr</footnote>

<footnote>*corresponding author</footnote>
finger lengths of 420 µm and 620 µm, these lengths were paired with active area, specifically 15.6mm² for large devices and 2.12 mm² for small BJT's, as detailed in Table 1. A maximum breakdown voltage of 11 kV was obtained in vacuum conditions with a high-voltage source [5].

<figure><img src="image_3.png" /><figcaption>Fig.1: Cross-section of the studied 4H-SiC 10 kV BJT</figcaption></figure>

<table><thead><tr><td>Finger Length (µm)</td><td>Die area (mm²)</td></tr></thead><tbody><tr><td>420</td><td>2.12</td></tr><tr><td>420</td><td>15.6</td></tr><tr><td>640</td><td>15.6</td></tr></tbody></table>

Table 1: Summary of the different BJT configurations, square dies

## Experimental Setup for Static Characteristics

The setup involves the static characterization of 4H-SiC BJTs using a B1505A, capable of handling up to 20 A in pulsed mode for the collector, 1 A for the base, and 3 kV in blocking mode, alongside a Thermal Conditioner Thermonics T2500/300E for temperature control from -50 °C up to 225 °C. Three samples were characterized with their respective finger length and active area. Measurements include applying a voltage sweep $V_{CE}$ and measuring IC for different fixed values of IB from 0.1 A to 1 A to obtain the output characteristic curves. By analyzing these curves, we can assess the transistor behavior in different operating regions and extract key parameters like, current gain, $\beta$.

## Results and Analysis of the static characteristics

The small and large BJTs exhibit similar on-state resistance per unit area as shown in Fig.2. Both devices achieved approximately 55 A.cm⁻² for collector current density with comparable base-current densities, 3.3 A.cm⁻² to 3.2 A.cm⁻², respectively corresponding to different base currents (70 mA and 0.5 A respectively). This observation suggests that the active area does not significantly impact the electrical characteristics concerning current density. Therefore, regardless of the physical size of the BJTs, their performance in terms of current density remains the same.

From Fig.3, we can observe that the current gain, $\beta$, is very similar between large and small BJTs (420 µm finger length, 15.6 mm² and 420 µm finger length, 2.12 mm²). A similar trend
is noticed between large BJT's with different finger length (640 µm and 420 µm), both having
a 15.6 mm² area.

<figure><img src="image_4.png" /><figcaption>Fig. 2: J<sub>C</sub> (V<sub>CE</sub>) for different J<sub>B</sub> at 25°C for a small (open symbol) and large (closed symbol) BJT, finger length of 420 µm</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Fig. 3: Extracted β for 4 different BJT's (finger length and area) at 25°C</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 4: Extracted β for the large BJT (finger length 420 µm, from square symbol on Fig. 4) for a temperature range of -50 °C to 150 °C</figcaption></figure>

Additionally, the current gain of the large BJT's tends to increase with decreased temperature as seen in Fig. 4. This increase is as a result of the reduced recombination rate of charge carriers due to lower thermal energy, which means fewer charge carriers recombine, more contribute to the current. Consequently, a smaller base current is required to control a given collector current, effectively enhancing the transistor's amplification capacity. This implies that at lower temperatures, the BJT's become more efficient in amplifying the base current
Experimental Setup for Switching Characteristics

<figure><img src="image_7.png" /><figcaption>Fig. 5: Double pulse test schematic diagram for switching characteristics on the 4H-SiC BJTs</figcaption></figure>

To investigate the switching characteristic of the 4H-SiC BJTs, a double pulse test circuit was configured as per the provided schematic in Fig. 5. The setup includes a voltage supply (V<sub>IN</sub> from 100 V to 1000 V) a base driver is connected to the base of the SiC BJTs. A fast recovery diode and an inductor are used to manage the switching transitions and energy storage respectively. The different voltages (Base, Collector and Emitter), the Base current using a current probe and the collector current using a shunt resistance are measured at each V<sub>IN</sub> step to analyze the BJT switching performance.

**Results and Analysis of the Switching Characteristics**

Fig. 6 shows the behavior of I<sub>C</sub> and I<sub>B</sub> respect to time for the switching characteristics of the BJT samples. I<sub>C</sub> exhibits a sharp rise as the BJT turns on due to the inductance charging, reaching higher peaks with increased V<sub>IN</sub>. However, the current starts dropping from its peak indicating that the base current is insufficient to maintain the BJT in saturation mode, leading to a transition towards the linear mode. This is evident in the V<sub>CE</sub> graph in Fig. 7 where V<sub>CE</sub> drops rapidly during the initial turn-on and then stabilizes at a higher voltage as the device exhibit saturation.

<figure><img src="image_8.png" /><figcaption>Fig. 6: I<sub>C</sub> and I<sub>B</sub> versus time for various V<sub>IN</sub> steps</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>Fig. 7: V<sub>CE</sub> versus time for various V<sub>IN</sub> steps</figcaption></figure>
Fig. 8 shows how the current gain (β) initially spikes, indicating strong carrier injection but then decreases as a reflection of I<sub>C</sub> due to the linear mode.

<figure><img src="image_10.png" /><figcaption>Fig. 8: Extracted β versus time for various V<sub>IN</sub> steps</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Fig. 9: Extracted β for 3 different BJT's (finger lengths and area)</figcaption></figure>

Fig. 9 shows the variation of extracted β versus time for the 3 different large BJT's. A similar β is obtained between these 3 different BJT's. The values (17 and 18) are very similar to those obtained in the static mode (Fig. 3, 15 and 18). We can therefore conclude that the finger length and size have no impact on the current gain of the device even if it extracted in static or dynamic mode.

## Summary

This paper presents the static and dynamic characteristics of 10 kV 4H-SiC BJT's, which demonstrates promising electrical performance, making it suitable for high-efficiency applications in harsh environments and their performance improves at lower temperatures due to enhanced carrier dynamics. Similar extracted β have been obtained for both static and dynamic mode even with different finger lengths and areas of the BJT's.

## Acknowledgments

Authors thank the French Research National Agency (ANR) for financial support of HV-PhotoSw: ANR-18-CE05-0020-01

## References

[1] B. Asllani, P. Bevilacqua, H. Morel, D. Planson, L. V. Phung, B. Choucoutou, T. Lagier, and M. M. Guyennet "Static and Switching Characteristics of 10 kV-class Silicon Carbide Bipolar Junction Transistors and Darlingtonts" Materials Science Forum Vol. 1004 (2020) pp 923-932

[2] M. Nawaz, N. Chen, F. Chimento and L. Wang "Static and Dynamic Characterization of High-Power Silicon Carbide BJT Module" 2014 IEEE Energy Conversion Congress and Exposition (ECCE), Pittsburgh, PA, USA, 2014, pp. 2824-2831

[3] M. Hosseinzadehlish, S. Jahdi, C. Shen, X. Yuan, I. Laird, O. Alatise, J. O. Gonzalez "Impact of Temperature and Base Bias Stress on the Static Characteristic of Silicon and 4H-SiC NPN Vertical BJT's" PCIM Europe 2023; International Exhibition and Conference for
Power Electronics, Intelligent Motion, Renewable Energy and Energy Management,
Nuremberg, Germany, 2023, pp. 1-9

[4] M.M.R. Ahmed, N-A.Parker-Allotey, P.A. Mawby, M. Nawaz and C. Zaring "Characterization Of The Static And Dynamic Behavior Of A SiC BJT" 2008 13th International Power Electronics and Motion Control Conference, Poznan, Poland, 2008, pp. 2472-2477

[5] A. Ammar, M. Lazar, B. Vergne, S. Scharnholz, L. V. Phung, P. Brosselard, D. Tournier, C. Sonneville, C. Raynaud, M. Zielinski, and al. "Design Fabrication and characterization of 10KV 4H-SiC BJT for Phototransistor Target. 2023 - Romanian Journal of Information Science & Technology - Vol.26, n°2, pp 193-204