Recently, the research group of Professor Wu Zhenping of the School of Science of Beijing University of Posts and Telecommunications, together with the research group of Professor Zhang Yang of Nankai University and the research group of Professor Hao Jianhua of the Hong Kong Polytechnic University, innovatively introduced lattice and band engineering regulation, and successfully developed a unipolar barrier type gallium oxide (Ga2O3)-based avalanche solar blind detector, which broke through the detection limit of existing solar blind ultraviolet detectors and reached the level of photomultiplier tubes in current commercial applications, providing new design ideas for the development of high-performance solar blind avalanche detectors, and related achievements.” Enhanced Gain and Detectivity of Unipolar Barrier Solar Blind Avalanche Photodetector via Lattice and Band Engineering” was recently published in the international academic journal Nature Communications.
As an ultra-wide bandgap semiconductor material that has attracted much attention in recent years, Ga2O3 has a band gap (~4.9 eV) that matches the solar blind band (200 – 280 nm), which is recognized as the most competitive material for the preparation of solar blind detectors, and has very important potential applications in the fields of ozone hole detection and ultraviolet communication. The 2021 Research Frontier Heat Index of the Chinese Academy of Sciences & Clarivate also listed “Ga2O3-based solar blind ultraviolet photodetector” as one of the top ten frontier research hotspots in physics. However, the previously reported Ga2O3 base solar blind detector performance still lags behind the current commercial photomultiplier tube (PMT), and how to further improve the device performance is an important issue in the field of solar blind detection. Due to the difficulty of p-type gallium oxide implementation and the constraints of lattice and band matching, the traditional p-n-type gallium oxide avalanche detector has not been reported, and the current research mainly focuses on the avalanche detector based on n-n heterojunction. To further improve the avalanche gain of the device, a Ga2O3 heterojunction with a large barrier height is constructed. At the same time, the materials that form the heterojunction need to have good lattice matching, otherwise defects at the interface will greatly affect the performance of the device. Therefore, the in-depth development of high-performance Ga2O3 dayblind detectors requires comprehensive consideration of the above problems.
Band structure diagram (from the research group)
In order to further improve the performance of the Ga2O3-based detector, after continuous exploration, the team adjusted the barrier height by inserting a suitable wide bandgap material (MgO), and successfully developed an n-Barrier-n unipolar barrier type avalanche photodetector (APD) composed of β-Ga2O3/MgO/Nb:SrTiO3 heterojunction, whose large conduction band offset increases the reverse breakdown voltage and significantly suppresses the dark current. The very small valence band shift facilitates the flow of minority carriers in the heterojunction. The device achieves avalanche gain of up to 5.9 × 105 and a specific detection rate of 2.33 × 1016 Jones, which is comparable to the commercial photomultiplier tubes widely used today.
Performance comparison chart (from the research group)
This study creatively proposes a method for regulating and designing n-B-n unipolar barrier Ga2O3 avalanche detectors through lattice and band engineering, which successfully improves the device performance, and the device performance involved in this study demonstrates the great potential of Ga2O3 in the next generation of optoelectronic devices of power devices. This pioneering design also provides new ideas for future research on higher performance Ga2O3 electronic devices.
This work is jointly completed by Beijing University of Posts and Telecommunications, Nankai University and Hong Kong Polytechnic University. Zhang Qingyi, a doctoral student in the School of Science, Beijing University of Posts and Telecommunications, is the first author of the paper, and Professor Wu Zhenping of Beijing University of Posts and Telecommunications, Professor Zhang Yang of Nankai University and Professor Hao Jianhua of The Hong Kong Polytechnic University are the co-corresponding authors of the paper. The research was supported by the National Natural Science Foundation of China, the State Key Laboratory of Information Photonics and Optical Communications Foundation, the Tianjin Natural Science Foundation, the Central Universities Basic Research Funds Special Fund, and the Hong Kong Research Grants Council.
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