Biography: Dr. Ye Yuan is currently an associate investigator in Songshan Lake Materials Laboratory, Guangdong, China. He received his B.S. and M. S degree in Harbin Institute of Technology. In 2017, he got his PhD from Technische Universität Dresden. Afterwards, he started his postdoc carrier in Helmholtz-Zentrum Dresden-Rossendorf and King Abdulla University of Science and Technology. He has joined Songshan Lake Materials Laboratory since 2019. His main research interests focus on the industrial preparation and application of ultra-wide bandgap semiconductors, e. g. AlN and BN. Dr. Ye Yuan has published more than 100 peer-reviewed papers. He has been authorized 18 invention patents, and two of them have been transferred at a value of 21 million ￥. He is now undertaking now 6 projects, including the general project of National Natural Science Foundation and research topic of National R&D program, etc.

Preparation and application of single-crystalline aluminum nitride template

Ye Yuan

Songshan Lake Materials Laboratory, China

Abstract: Aluminum nitride has great potential in deep ultraviolet light-emitting devices, high-power power electronic devices and high-frequency microelectromechanical systems (MEMS) due to its ultra-wide direct band gap (~6.2 eV) and c-axis high-frequency piezoelectric properties. With its application prospects, it is called the "fourth generation semiconductor" together with diamond, boron nitride, etc. In response to the current bottleneck problem of difficult and expensive aluminum nitride single crystal bulk substrate preparation, we have successfully developed 2 to 6-inch aluminum nitride single crystal composite substrates using physical vapor deposition high-temperature annealing. This method enables the template to exhibit low-cost, low-dislocation-density (<5×10⁸ cm^-2), smooth surface (showing atomic step flow morphology, RMS≤0.2 nm), good repeatability and high yield. In addition, we have successfully controlled the stress state in the aluminum nitride single crystal composite substrate, enabling it to achieve technological breakthroughs in a variety of major application scenarios:

(i) Based on the 4-inch AlN single-crystalline template, we have realized for the first time 4-inch low-cost deep ultraviolet LED epitaxial wafer with flat surface, and have significantly reduced the thickness of AlN buffer layer from 3 μm to 150 nm for the first time, which greatly reduces production costs, allowing the current expensive deep ultraviolet epitaxy technology to be seamlessly connected with the mature blue LED epitaxy process.

(ii) It is achieved that an ultra-thin structure HEMT power device with a withstand voltage exceeding 2600V based on the AlN single-crystalline template, opening the door for gallium nitride power electronic devices to move from the original 650V low-voltage application into the 1200~1700V medium-voltage application.

(iii) On the basis of post-annealed a-plane AlN single-crystalline template, a high performance resonator is achieved: The Rayleigh surface acoustic wave at 2.38 GHz exhibits a quality factor as high as 3731 and an insertion loss as low as 39 dB. Moreover, a laterally excited bulk wave with resonant frequency of 4.00 GHz was successfully excited by using only planar interdigital electrodes, demonstrating the potential of AlN single-crystalline template in the field of MEMS.

[1] Shangfeng Liu, et al., J. Semicond., 42, 122804 (2021)

[2] Shangfeng Liu, et al., Adv. Func. Mater., 32, 2112111 (2022)

[3] Xiaoli Fang et al., 2023 IEEE International Ultrasonics Symposium (IUS), Montreal, Canada, Sep. 2023

[4] Tongxin Lu et al., Appl. Phys. Lett.,123, 252105 (2023)