【Domestic News】Shandong University Successfully Developed High Quality 4-inch Ga₂O₃ Crystal

  Recently, Professor Tao Xutang's team of Shandong University successfully prepared 4-inch (001) main surface gallium oxide single crystal with complete shape using Edge-defined Film-fed Growth (EFG), and its properties are analyzed. Laue diffraction pattern is clear and symmetrical, indicating that the crystal has good single crystal property and no twinned; The rocking curve of X-ray diffraction shows that the full width at half maximum of (400) face is only 57.57 ″, and the crystal quality is high; The results of wet chemical etching test show that the crystal dislocation density is 1.06 × 10⁴ cm^-2； C-V test confirmed that  the carrier concentration in β-Ga₂O₃ crystal is 7.77×10¹⁶ cm^-3. The test results show that the team has obtained high-quality 4-inch β-Ga₂O₃ single crystal. The achievement entitled "Research on the Growth and Properties of 4-inch Ga₂O₃ Single Crystal" was first published on the Internet of Journal of Artificial Crystals (DOI: 10.16553/ j.cnki.issn1000-985x. 20220831.001.). This achievement is another breakthrough after the team obtained 4-inch (100) main plane single crystal in 2019.

Figure 1: 4-inch β-Ga₂O₃ crystal

Figure 2:  Laue diffraction pattern of (010) plane of β-Ga₂O₃ single crystal

Figure 3: Rocking curve of β-Ga₂O₃ single crystal

  In addition, by optimizing the Czochralski crystal growth process, the team successfully magnified the original 1-inch crystal to 2-inch, with high crystal quality and regular crystal shape,without cracks. The crystal growth size is equivalent to that of Germany IKZ and the US Air Force Laboratory, reaching the international advanced level.

Figure 4: 2-inch Ga₂O₃ single crystal columnar grown by Czochralski method

  The State Key Laboratory of Crystal Materials of Shandong University was the first to develop Ga₂O₃ single crystal growth by the method of Edge-defined Film-fed Growth (EFG) in China. After a long period of dedicated research, from scratch, it has successively broken through the key core technologies of 1~4 inch Ga₂O₃ single crystal, such as growth, defects, doping, processing, etc. n-type conductive and semi insulating gallium oxide crystals were grown by Edge-defined Film-fed Growth (EFG), Czochralski method and other crystal growth methods, and systematic crystal processing and defect research were carried out, which laid a foundation for breaking the foreign technology blockade and product embargo.

  As an ultra wide band gap semiconductor material, β-Ga₂O₃ can be used to prepare power devices, ultraviolet detectors, high-energy ray detectors, as well as as the substrate material of GaN, ZnO and other semiconductors. Due to the ultra-high breakdown field strength and Baliga’s figure of merit, β-Ga₂O₃ power devices have the advantages of high voltage resistance, low conduction loss and fast switching speed. At present, the voltage resistance of both β-Ga₂O₃ diode and its field effect transistor devices can reach several thousand volts, and the strength of device breakdown field has exceeded the theoretical limit of SiC and GaN.

  Due to the band gap of β-Ga₂O₃ is 4.8 eV, the absorption cut-off edge is at 260 nm, the UV transmittance can reach more than 80%, and it has good chemical stability and thermal stability. Therefore, β- Ga₂O₃ crystal itself meets the needs of "solar blind" photoelectronic devices, avoiding some complex problems at present, for example, common nitrides need to alloy. Due to its excellent material properties, β-Ga₂O₃ crystal has important applications in deep ultraviolet photoelectric detection and ultra-high voltage power devices. It is also the key material that the United States and other western countries have recently imposed an embargo on China.

Source: Contributed by the State Key Laboratory of Crystal Materials of Shandong University

Author: Mu Wenxiang/Jia Zhitai/Tao Xutang (Shandong University, State Key Laboratory of Crystal Materials, New Generation Semiconductor Materials Research Institute; Crystal Materials Research Institute)