Recently, China has made a major breakthrough in the electronic components industry. The third-generation semiconductor team of Songshan Lake Materials Laboratory, Professor Zhang Jincheng and Professor Li Xiangdong of Academician Hao Yue's research group of Xidian University, and Guangdong Zhineng Technology Co., Ltd. jointly tackled key problems and successfully prepared high-performance GaN HEMTs wafers based on 2~6-inch AlN single crystal composite substrates. This achievement is due to the significant material advantages of the AlN single crystal composite substrate, which has a dislocation density as low as 2×10^8 cm^-2, which reduces the thickness of the AlGaN buffer layer to 350 nm, greatly reduces the epitaxial cost and effectively controls the wafer warpage.
In the course of the study, the team found that the Si and O impurities present on the surface of the AlN single crystal composite substrate can lead to parasitic leakage channels, which affect the normal shutdown of HEMTs devices. In order to solve this problem, the team innovatively proposed a secondary growth AlN buried layer method to cover the impurity layer so that it cannot be ionized in the ultra-wide bandgap material, thereby significantly inhibiting the leakage. The experimental results show that the transverse breakdown voltage of the undoped ultra-thin AlGaN buffer layer can easily exceed 10 kV, the closed-state withstand voltage of the HEMTs device exceeds 8 kV, the dynamic current collapse is less than 20%, and the threshold voltage drift is less than 10%, and the reliability evaluation has been preliminarily passed.
The results have been published in the top journals in the field of devices, IEEE TED (DOI: 10.1109/ISPSD59661.2024.10579573) and ISPSD (DOI: 10.1109/ISPSD59661.2024.10579573). This breakthrough is of great significance for the preparation and application of large-size new substrates in China, and provides strong support for the development of the third generation of semiconductor technology.
Figure: GaN wafer fabricated on 6-inch AlN monocrystalline composite substrate, transfer characteristic curve, dynamic output characteristicscurves and dynamic transfer characteristic curves
