【Domestic News】Team of Professor Yang Jiayue from Shandong University : Based on the First Principle, Study on Electron Transport Properties in β-(AlₓGa₁₋ₓ)₂O₃ Alloy

  As a new wide band gap semiconductor, gallium oxide（ β-Ga₂O₃) has high band gap width (Eg=4.6-4.9 eV), high electrical breakdown voltage, controllable n-type doping and the availability of high-quality substrate, and it has great application prospects in power appliances, solar concealed ultraviolet photodetectors, and novel sensor technologies. In recent years, researchers have made great progress in the modification of gallium oxide. For example, extensive band gap adjustment (4.8-8.8 eV) can be achieved by alloying Ga₂O₃ and Al₂O₃, which shows that β-Ga₂O₃ has higher breakdown electric field compared with AlGO alloy.

  The electronic structure of AlGO alloy, such as energy band and density of states, has been widely studied, but its carrier transport properties are difficult to accurately study due to its complex structure. Therefore, we combine the first-principles calculation method and the Boltzmann transport equation to accurately predict their carrier (electron) mobility and clarify their internal scattering mechanism.

  There are two kinds of coordination in β-Ga₂O₃ crystal structure, octahedral coordination and tetrahedral coordination. Research shows that Al preferentially occupies octahedral coordination in the process of alloying. Based on this alloy rule, we have constructed AlGO alloys with a proportion of 25% and 50%, as shown in Figure 1.

  The carrier mobility results are shown in Figure 2. At low temperature, the ionized impurity scattering of AlGO alloy plays a dominant role in the scattering mechanism. With the increase of temperature, its effect decreases and the low polarity optical phonon scattering plays a major role. The theoretical prediction trend is in good agreement with the existing experimental data. Calculation results show that the electron mobility of β-(Al_0.25Ga_0.75) ₂O₃ and β- (Al_0.5Ga_0.5) ₂O₃ alloy are 103.6 and 80.60 cm²/V s at 300 K, respectively. Such low electron mobility is affected by the inherent strong polar optical phonon scattering. Moreover, with the further increase of aluminum content, the Fourier Constant and the intensity of polar phonon scattering increases, resulting in the further reduction of the electron mobility of the alloy. This work provides a way to understand the electronic transport properties of AlGO alloys, and provides a theoretical basis for improving the electronic mobility of potential applications in high-power electronic devices.

Introduction of the Team Leader

  Yang Jiayue, professor and doctoral supervisor of Shandong University, was selected in the list of  the National Overseas Youth Talent. Studying in Harbin University of Technology from 2006 to 2015, he successively obtained a bachelor's degree in electronic science and technology, a doctor's degree in engineering thermophysics, and won the excellent doctoral thesis of the 18th Harbin University of Technology; Later, he went to the Institute of Minerals, Aachen University of Technology, Germany, for post-doctoral research; He returned to China in November 2018 and started scientific research and teaching at Shandong University, and was selected as the national high-level overseas youth talent in 2020.His current research directions are: high-temperature thermal radiation thermophysical properties, thermal conductivity multi-scale simulation and engineering control, thermal management of wide band gap semiconductor devices, microwave characteristics of high-temperature ceramics and intelligent design of functional materials. In recent years, more than 40 of his SCI papers have been published in world-class journals of engineering thermophysics such as JPCL, PRB, APL, OL, JQSRT, etc; He has applied for 4 invention patents (including 2 authorized patents and 1 accepted US patents). During his post-doctoral work in Germany, he was supported by the Youth Fund of Aachen University of Technology in Germany and the Ulrich Supercomputing Research Center in Germany. He has undertaken or mainly participated in projects such as the National Defense Key Laboratory Fund, GF Science and Technology Innovation Zone H863 and Equipment Pre-research Key Laboratory.