【Expert Interview】Prof. Han Genquan's team invented advanced technology to effectively solve the heat dissipation bottleneck of Gallium Oxide power devices, helping the industry industrialization!

Expert Profile

      Han Genquan, born in April 1979, winner of the National Outstanding Youth Fund, second-level professor of Xidian University, selected high-level talents of Shaanxi Province, leader of Zhejiang Province's leading innovation and entrepreneurship team. He received his bachelor's degree from Tsinghua University and his Ph. D. degree from Institute of Semiconductors of Chinese Academy of Sciences. After that, he was engaged in microelectronic device research at the National University of Singapore for many years. He returned to China in 2013 and worked in Chongqing University, Xidian University and Xidian University Hangzhou Research Institute successively. Professor Han Genquan has made a series of important research achievements in microelectronics: 1) Innovative invention of several new ferroelectric materials, achieving the highest polarization reversal durability; 2) Innovative invention of high-performance, low-power FeRAM and FeFET memory and memory chips, breaking the monopoly of foreign technology; 3) Invented and developed GeSn channel transistor with high mobility; 4) Original invention ion knife technology to achieve wafer-level heterogeneous integration of Gallium Oxide materials and devices, which can completely solve the thermal bottleneck of Gallium Oxide power devices. Published more than 300 articles in micro/optoelectronics flagship journals and conferences IEDM/VLSI, Nature Communications, IEEE EDL, AFM, etc., and applied for/authorized more than 70 patents, including more than 20 cover articles of various types. He has been cited by Google Scholar 5239 times, and made more than 30 invited reports and reviews at international conferences. He has won the Shaanxi Youth Science and Technology Award, the Excellent Tutor Award of the Electronics Society, the second prize of the Yangtze River Delta-Guangdong-Hong Kong-Macao Greater Bay Area Integrated Circuit Entrepreneurship Competition, etc. He has guided students to win the best student paper of ICSICT, SSDM and other international conferences. He is currently the editor of IEEE Electron Device Letters, the editor of National Science Open, and the deputy editor of the Journal of Semiconductors.

AGOA：The teacher's team briefly introduced, the current research direction, research progress, research results and so on

      As the director of the laboratory, Professor Han Genquan established the Intelligent Chip and Microsystem Laboratory in XIdian University Hangzhou Research Institute, and hired Academician Hao Yue as the chief consultant of the laboratory. At present, the laboratory has 27 members, including 4 national-level talents. More than half of The members are from UC Berkeley, The University of Tokyo, Warwick University, National University of Singapore and the University of Hong Kong The team has strong academic innovation ability, rich experience in device and chip development, strong team cohesion and positive and warm scientific research atmosphere. The research team is determined to contribute to the cause of integrated circuits in China, contributing wisdom and strength.

Research direction: Intelligent chip and microsystem technology

Research progress and Achievements:

1）Aiming at the inherent bottleneck problem of Gallium Oxide, which has low thermal conductivity, the project team innovatively proposed a heterointegration technology of high thermal conductivity substrate, and realized SiC and Si based high-performance heterointegration β-Ga₂O₃ MOSFETs, and systematically studied their structural design, preparation process, and physical mechanism of device electrical and thermal transport. The relevant results were published in IEDM, an important conference in the field of microelectronics, Science China Physics, Mechanics & Astronomy, IEEE Electron Device Letters/IEEE Transactions on The relevant technical achievements have been patented and some of them have been authorized in well-known journals such as Electron Devices.

2）In response to the difficulties of Ga₂O₃'s current lack of P-type materials and the contradiction between the breakdown electric field and the on-resistance, the concept of superjunction structure was innovated. Based on p-NiO/n-Ga₂O₃ heterojunction, surface electric field lowering structure (RESURF) and superjunction (SJ) structure β-Ga₂O₃ MOSFETs were designed. And the preparation of RESURF and SJ-β-Ga₂O₃ MOSFETs was preliminarily realized. The experimental results show that the design of superjunction structure restructures the electric field distribution of the device, and the prepared SJ-β-Ga₂O₃ MOSFETs have significantly improved the breakdown voltage, power quality factor (PFOM) and other key indicators compared with conventional devices of the same size. This work is reported in IEDM 2021, IEEE Transactions on Electron Devices, and is included in The top ranked student papers of IEDM 2021.

3）The interface optimization of Gallium Oxide is studied to solve the interface problem, which is one of the most difficult problems in power devices. The low-temperature oxygen annealing interface enhancement program, the crystalline AlGaO insertion layer optimization program and the composite passivation repair program have been developed successively to repair and passivate the defect on the Gallium Oxide surface and the defect on the channel interface of the Gallium Oxide transistor, thereby improving the interface quality, greatly reducing the interface defect density, and promoting the comprehensive performance of Gallium Oxide power devices. Some of the results have been published in Appl. Phys. Lett., IEEE IEEE Transactions on Electron Devices and other journals.

AGOA：the team to study the current difficulties, or recently cracked difficulties

      The advantages of Gallium Oxide semiconductors are outstanding, but the low thermal conductivity of materials is still a bottleneck problem when it is applied to power devices, which seriously restricts the performance of Gallium Oxide power devices. The low thermal conductivity makes the heat generated by the Gallium Oxide devices unable to dissipate effectively from the substrate, resulting in a sharp increase in junction temperature and serious degradation of performance. Therefore, low thermal conductivity has become one of the biggest bottlenecks restricting the industrial application of Gallium Oxide in the direction of power devices, and is also the core direction of domestic and international Gallium Oxide technology research. The team has been committed to solving the thermal bottleneck of Gallium Oxide technology and promoting the industrialization of Gallium Oxide technology. Focusing on this goal, the team takes the heterogeneous integration of "Gallium Oxide thin-film and high thermal conductivity substrate" as the starting point, combined with the characteristics of Gallium Oxide single crystal material, and has carried out technical research on the stripping and integration technology suitable for Gallium Oxide single crystal for a long time. Through collaborative optimization of key parameters such as ion injection dose, bonding method, and stripping temperature, the team recently successfully developed a smart stripping technology for Gallium Oxide single crystal wafers. This technology can effectively peel large area, wafer-level single crystal thin films from Gallium Oxide wafers to achieve "Gallium Oxide thin-film - any target substrate" wafer-level heterogeneous integration. In addition to the important goal of integrating a Gallium Oxide film with a high thermal conductivity substrate, this technology has unique advantages in that the substrate material is not limited by lattice matching, and the stripped Gallium Oxide wafers can be recycled, which can further develop more complex high-quality Gallium Oxide thin film structures and reduce the cost of Gallium Oxide.

      Based on this technology, the team for the first time in the world based on Silicon Carbide and Silicon substrate innovation to prepare large size, high thermal conductivity Gallium Oxide heterointegrated wafers, has successfully achieved 2-4 inch Gallium Oxide heterointegrated wafers. According to systematic characterization, the crystal mass and electrical conductivity of the heterogeneous integrated Gallium Oxide films are comparable to that of the Gallium Oxide single crystal substrate, the film transfer rate is higher than 95%, the thickness non-uniformity is less than 2%, and the surface roughness is lower than 0.2 nm. The overall heat dissipation performance of the heterogeneous epitaxial Gallium Oxide films reported at the same time is much better than that of the substrate materials (such as Silicon Carbide). Basically meet the needs of industrialization.

AGOA：optimistic about the development potential of Gallium Oxide

      Gallium Oxide semiconductor devices have ultra-wide band gap, ultra-high voltage threshold, excellent power and radio frequency characteristic factors and large-scale production potential, which can meet the development needs of the energy electronics market for high efficiency, integration, miniaturization and economy of power devices. On the basis of the technical solution of heterogeneous integrated Gallium Oxide wafers, the heat dissipation bottleneck of Gallium Oxide devices will be effectively overcome, and it is expected that Gallium Oxide transistors, diodes and other devices will have higher application potential as core power electronic components in the future in the smart grid management control system, large-scale energy storage conversion system, and more integrated automotive electronics and photovoltaic inverter fields.

AGOA：the direction of training talents in the school, how to better train high-quality talents?

      The Gallium Oxide industry belongs to the field of pan-semiconductor, involving many specialized fields such as materials, equipment and manufacturing, which poses a great challenge for school training in teaching practice. In terms of cultivating talents, I think we should grasp both basic literacy and innovative ability. Basic literacy is to train students based on the basic knowledge of the industry, while taking into account a wide range of subject knowledge, to train students' literacy; On this basis, for students who are interested in continuing to study in this industry, further develop progressive innovative knowledge training, so that students have the opportunity to grow into key talents who can lead the development of the industry while obtaining basic literacy.

AGOA：How to view the role of school-enterprise cooperation and the combination of industry, university and research in the development of Gallium Oxide industrialization

      School-enterprise cooperation or industry-university-research through mode will become the mainstream of the entire pan-semiconductor industry in the future. Gallium Oxide technology is now in the nascent stage. At this critical juncture, the advanced nature of Gallium Oxide related technologies can be guaranteed at the source, the technical route can be better planned, and the sound development of the industry can be promoted by combining the innovative resources of universities and research institutes with the industrial demand.

AGOA：Is there any project that needs to transform the results?

      The team invented the intelligent stripping and heterogeneous integration technology applicable to Gallium Oxide, realizing the heterogeneous integration of Gallium Oxide materials and devices at the wafer level, which can effectively solve the heat dissipation bottleneck of Gallium Oxide power devices. Gallium Oxide heterointegrated wafers can be directly used for device preparation, and are superior to monolithic Gallium Oxide wafers in process complexity and material properties. This technology has passed the pilot stage and can be mass-produced 2-4 inches of Gallium Oxide heterointegrated wafers to solve the heat dissipation problem that has troubled the industrialization of Gallium Oxide devices for a long time. This technology is seeking to transform the results.

AGOA：What kind of support do you want the Alliance to provide?

      It is suggested to increase the public communication platform, which can carry out online communication channels such as scholar forums, student sharing and discussion forums, so as to enable more people to participate effectively, provide more communication opportunities for practitioners, provide more learning opportunities for beginners, and expand the overall research team and concern group.