【Member News】Nature · Communication Reported that Academician Hao Yue's Team Has Developed the World's Highest Power of 13.2 GW/cm² Ga₂O₃ Diode and Realized Holes Injection Effect in Ga₂O₃ for the First Time

    Recently, Professor Zhang Jincheng and Professor Zhou Hong, members of the R&D team of academician Hao Yue from Xi'an University of Electronic Science and Technology, have made important progress in the research of ultra wide band gap semiconductor Ga₂O₃ power devices, and developed a new type of p-NiO/n-Ga₂O₃ semiconductor heterostructure diode with the method of holes injection. Through holes injection, this structure realizes a Ga₂O₃ power diode with ultra-high voltage withstand and extremely low on-resistance. Its power value reaches 13.2GW/cm², which is the highest of Ga₂O₃ semiconductor devices up to now. Related achievements were published in the international journal Nature Communication entitled Ultra wide band-gap semiconductor Ga₂O₃ power diodes.

    Gallium oxide（ β-Ga₂O₃) is a typical representative of ultra wide band gap semiconductor. With its band gap width as high as (~4.8 eV),and the critical breakdown field strength as high as (~8 MV/cm), it is one of the ideal semiconductor materials for developing high withstand voltage , high power and efficient energy-saving semiconductor devices. It can realize the triple advantages of device chips, which are high breakdown, low power consumption and low cost. It has significant application prospects in power transmission and conversion, electric vehicles, high-speed rail and other fields. Compared with the  third generation semiconductor GaN and SiC in the current industry, Ga₂O₃ power devices have lower on resistance under the same withstand voltage, which will achieve lower power consumption and higher conversion efficiency when applied to the field of electric energy conversion. Therefore, in recent years, gallium oxide semiconductor has become the international research hot spot of semiconductor and the commanding height of technology competition in power countries.

    Since 2018, under the leadership of Academician Hao Yue, Xi'an University of Electronic Science and Technology has achieved a high-speed improvement in the performance of gallium oxide power diodes and power transistors through a series of technological innovations such as independent gallium oxide growth MOCVD equipment, high-quality gallium oxide epitaxial materials, new structures and new processes of high-voltage devices. As shown in Figure 1 and 2, Xi'an University of Electronic Science and Technology has achieved a number of milestone achievements, making the research level of gallium oxide power devices in China enter the forefront of the world.

Fig. 1 Research progress of Ga₂O₃ power diode in Xi'an University of Electronic Science and Technology

Fig. 2 Research progress of Ga₂O₃ power transistors in Xi'an University of Electronic Science and Technology

    Due to the difficulty of p-type doping and low hole mobility, the bipolar carrier transport and conductivity modulation effect in Ga₂O₃ power devices have not been achieved, which is the main obstacle restricting the further improvement of Ga₂O₃ power devices.Therefore, a new p-NiO/n-Ga₂O₃ heterojunction PN junction diode structure was constructed in this work, as shown in Figure 3 (a).

    On the one hand, by combining PN heterojunction, magnesium into terminal, high k/low k Poisson terminal field plate, high temperature thermal annealing is used to suppress unintentional doping, the peak electric field strength of the device is greatly weakened, as shown in Figure 3 (b); It has started a new technical access for the development of high voltage withstand gallium oxide devices, realizing the high breakdown voltage of 8.3 kV, as shown in Figure 3 (c).On the other hand, thanks to the design of low conduction band of PN heterostructures, the ultra wide band gap PN heterostructure power diode achieves a low switching-on.With the forward bias, the hole barrier decreases, and the p-region hole jumps over the PN heterojunction into the n-region. When the hole concentration is higher than the electron concentration, the electron concentration is to rise, which significantly reduces the resistance of the device, as shown in Figure 3 (d).With the increase of the forward voltage, the resistance continues to decrease, and the hole superinjection effect is realized in Ga₂O₃ devices.The developed Ga₂O₃ power diode has ultra-high withstand voltage and extremely low resistance, and the power excellent value P-FOM is up to 13.2 GW/cm², which is the highest value of Ga₂O₃ semiconductor devices up to now.

Fig. 3（a）Three dimensional structure diagram of the device,（b）electric field diagram obtained by simulation of different device structures under 8.3 kV withstand voltage,（c）breakdown voltage diagram of the device ,（d）forward conduction diagram of the device ,（e）Resistance-withstand voltage comparison diagram of ultra wide band gap semiconductor power devices.