Bioelectronics
Department of Microelectronics

Shaogang Wang

Publications

  1. Effects of Current Filaments on IGBT Avalanche Robustness: A Simulation Study
    Jingping Zhang; Houcai Luo; Huan Wu; Bofeng Zheng; Xianping Chen; Guoqi Zhang; Paddy French; Shaogang Wang;
    Electronics,
    2024. DOI: https://doi.org/10.3390/electronics13122347
    Keywords: ... IGBT; avalanche; current filament; robustness; SOA.

    Abstract: ... With the increase in voltage level and current capacity of the insulated gate bipolar transistor (IGBT), the avalanche effect has become an important factor limiting the safe operating area (SOA) of the device. The hole injection into the p/n junction on the backside of the IGBT after avalanche is the main feature that distinguishes the avalanche effect from other devices. In this paper, the avalanche breakdown characteristics of IGBT and the nature of current filament are investigated using theoretical analysis and numerical simulation, and the underlying physical mechanism controlling the nature of current filaments is revealed. The results show that the hole injection on the backside of the IGBT leads to an additional negative differential resistance (NDR) branch on the avalanche breakdown curve. The device’s common-base current gain, αpnp, is a crucial factor in determining the current filament. As αpnp increases, the avalanche-induced current filament becomes stronger and slower, resulting in weaker avalanche robustness of the device.

  2. FLEXIBLE HIGH-SENSITIVITY STRAIN SENSOR FABRICATED WITH PDMS MICRO-CHANNEL ARRAY USING LASER TRANSMISSION PYROLYSIS TECHNOLOGY
    Shaogang Wang; Qihang Zong; Huiru Yang; Qianming Huang; Huaiyu Ye; Paddy French;
    In IEEE (Ed.), IEEE MEMS 2024,
    IEEE, January 2024.
    Keywords: ... Stretchable strain sensor, Metal film, UV laser, Laser transmission pyrolysis, PDMS pattering.

    Abstract: ... In recent years, flexible strain sensors based on metal cracks have garnered significant interest for their exceptional sensitivity. However, striking a balance between sensitivity and detection range remains a significant challenge, which often limits its wider application. Herein, we introduce an innovative laser transmission pyrolysis technology to fabricate high performance flexible strain sensors based on (Au) metal cracks with a microchannel array on the PDMS surface. The fabricated flexible strain sensors exhibit high sensitivity, wide detection range, precise strain resolution,fast response and recovery times, and robust durability. Furthermore, this technology has potential applications in microfluidics, microelectromechanical systems and optical sensing.

  3. Advanced NO2 Gas Sensor Fabrication through UV Laser-Induced Selective Reduction Laser Sintering
    Shaogang Wang; Qihang Zong; Huiru Yang; Qianming Huang; Huaiyu Ye; Paddy French;
    In IEEE NEMS 2024,
    Kyoto, Japan, 2024.

  4. Chitosan Oligosaccharide Laser Lithograph: A Facile Route to Porous Graphene Electrodes for Flexible On-Chip Microsupercapacitors
    Qian-Ming Huang; Huiru Yang; Shaogang Wang; Guoqi Zhang; Paddy French; Huaiyu Ye;
    In Proceedings IEEE NEMS 2024,
    IEEE, IEEE, May 2024.

  5. Reliability Analysis of Cu Sintered Die-Attach for SiC Power Devices: Mechanical, Electrical, and Thermal Evaluation
    Xu Liu; Shaogang Wang; Dong Hu; Chenshan Gao; Qianming Huang; Huaiyu Ye; Paddy French; Guoqi Zhang;
    In IEEE 74th Electronic Components and Technology Conference (ECTC),
    Denver, Colorado, IEEE, IEEE, May 2024.

  6. Reverse Recovery Optimization of Multiepi Superjunction MOSFET Based on Tunable Doping Profile
    Ke Liu; Chunjian Tan; Shizhen Li; Wucheng Yuan; Xu Liu; Guoqi Zhang; Paddy French; Huaiyu Ye; Shaogang Wang;
    Electronics,
    Volume 12, Issue 2977, 2023. DOI: https://doi.org/10.3390/electronics12132977
    Keywords: ... superjunction; MOSFET; doping profile; reverse recovery; body diode.

    Abstract: ... This paper proposes and simulates research on the reverse recovery characteristics of two novel superjunction (SJ) MOSFETs by adjusting the doping profile. In the manufacturing process of the SJ MOSFET using multilayer epitaxial deposition (MED), the position and concentration of each Boron bubble can be adjusted by designing different doping profiles to adjust the resistance of the upper half P-pillar. A higher P-pillar resistance can slow down the sweep out speed of hole carriers when the body diode is turned off, thus resulting in a smoother reverse recovery current and reducing the current recovery rate (dir/dt) from a peak to zero. The simulation results show that the reverse recovery peak current (Irrm) of the two proposed devices decreased by 5% and 3%, respectively, compared to the conventional SJ. Additionally, the softness factor (S) increased by 64% and 55%, respectively. Furthermore, this study also demonstrates a trade-off relationship between static and reverse recovery characteristics with the adjustable doping profile, thus providing a guideline for actual application scenarios.

  7. Rapid Fabrication of High-Performance Flexible Pressure Sensors Using Laser Pyrolysis Direct Writing
    Shaogang Wang; Qihang Zong; Huiru Yang; Chunjian Tan; Qianming Huang; Xu Liu; Guoqi Zhang; Paddy French; Huaiyu Ye;
    Applied Materials and Interfaces,
    2023. DOI: https://doi.org/10.1021/acsami.3c04290
    Keywords: ... flexible pressure sensor, UV laser, laser direct writing, continuous laser pyrolysis, PDMS, micro-truncated pyramid.

    Abstract: ... The fabrication of flexible pressure sensors with low cost, high scalability, and easy fabrication is an essential driving force in developing flexible electronics, especially for high-performance sensors that require precise surface microstructures. However, optimizing complex fabrication processes and expensive microfabrication methods remains a significant challenge. In this study, we introduce a laser pyrolysis direct writing technology that enables rapid and efficient fabrication of high-performance flexible pressure sensors with a microtruncated pyramid array. The pressure sensor demonstrates exceptional sensitivities, with the values of 3132.0, 322.5, and 27.8 kPa−1 in the pressure ranges of 0−0.5, 0.5−3.5, and 3.5−10 kPa, respectively. Furthermore, the sensor exhibits rapid response times (loading: 22 ms, unloading: 18 ms) and exceptional reliability, enduring over 3000 pressure loading and unloading cycles. Moreover, the pressure sensor can be easily integrated into a sensor array for spatial pressure distribution detection. The laser pyrolysis direct writing technology introduced in this study presents a highly efficient and promising approach to designing and fabricating high-performance flexible pressure sensors utilizing micro-structured polymer substrates.

  8. High-Performance Flexible Strain Sensor Fabricated Using Laser Transmission Pyrolysis
    Shaogang Wang; Huiru Yang; Qihang Zong; Qianming Huang; Chunjian Tan; Chenshan Gao; Shizhen Li; Huaiyu Ye; Guoqi Zhangand; Paddy French;
    IEEE Sensors Journal,
    2023. DOI: doi: 10.1109/JSEN.2023.3337233
    Keywords: ... Stretchable strain sensors, Metal film, UV laser, Laer transmission pyrolysis, PDMS pattering..

    Abstract: ... In recent years, metal crack-based stretchable flexible strain sensors have attracted significant attention in wearable device applications due to their extremely high sensitivity. However, the trade-off between sensitivity and detection range has been an intractable dilemma, severely limiting their practical applications. Herein, we propose a laser transmission pyrolysis technology for fabricating high-performance flexible strain sensors based on (Au) metal cracks with the microchannel array on the polydimethylsiloxane (PDMS) surface. The fabricated flexible strain sensors exhibit high sensitivity (gauge factor of 2448), wide detection range (59% for tensile strain), precise strain resolution (0.1%), fast response and recovery times (69 ms and 141 ms), and robust durability (over 3000 cycles). In addition, experiment and simulation results reveal that introducing a microchannel array enables the stress distribution strategy on the sensor surface, which significantly improves the sensing sensitivity compared to conventional flat surface sensors. Based on the excellent performance, the sensors are applied to detect subtle physiological signals such as pulse and swallowing, as well as to monitor large-scale motion signals such as knee flexion and finger bending, demonstrating their potential applications in health monitoring, human-machine interactions, and electronic skin

  9. Flexible and Highly Sensitive Pressure Sensor Based on Patterned PDMS Forming with Laser Pyrolysis Direct Write Technique for Wearable Electr
    Shaogang Wang; Qihang Zong; Chunjian Tan; Huaiyu Ye; Paddy French;
    In MNE 2022,
    September 2022.

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