【Member News】The research results of Yue Hao’s team on β-Ga₂O₃ power devices have been published in Applied Physics Letters

        With the increasingly widespread application of power electronics in fields such as automotive electronics, medical devices, and aerospace, the research and development of wide and ultra-wide bandgap semiconductor materials and devices have entered an accelerated stage. As a typical representative of the new generation of wide bandgap semiconductors, β-Ga₂O₃ has high breakdown field strength and low substrate manufacturing cost, which makes it an ideal material for power semiconductor devices. However, current research on the Ga₂O₃-based power diode mainly focus on increasing breakdown voltage and reducing specific on-resistance, while there is few study on the key parameter of turn-on voltage. High turn-on voltage will extremely increase the switching losses of power devices, which is not conducive to the practical application of Ga₂O₃-based power devices in the long run.

        To deal with this topic, Academician Yue Hao's team conducted a series of study on the impact of oxygen-containing plasma treatment on Ga₂O₃-based power diodes. By designing three types of devices (N₂O plasma treatment, O₂ plasma treatment, and without treatment), they compared and analyzed the effects of oxygen-containing plasma treatment on the turn-on voltage, specific on-resistance, breakdown voltage, and interface characteristics of β-Ga₂O₃ Schottky barrier diodes. The study found that N₂O plasma treatment can effectively reduce the turn-on voltage and improve the breakdown voltage of the device by reducing the trap states density.

FIG. 1. Schematic diagram and micrograph of plasma treated diode.

      Through the study of the forward IV characteristics of the devices, it was found that the turn-on voltage of devices with the N₂O plasma-treatment, O₂ plasma-treatment, and non-treatment are 0.6 V, 1.1 V, and 0.8 V, respectively. The specific on-resistance of each device are 3.5, 4.2, and 4.0 mΩ·cm², respectively. The diodes with N₂O plasma treatment showed effective reduction in both turn-on voltage and specific on-resistance. Through the study of the temperature stability of the devices, it was found that the device's forward voltage tends to decrease with increasing temperature. And the N₂O treated devices exhibited a significant increase in leakage current at 473K. Besides, the turn-on voltage of the O₂ treated devices showed a more variation with temperature.

FIG. 2. Forward IV characteristic curves of the devices

      Through X-ray photoelectron spectroscopy analysis, it was found that the diodes with N₂O plasma treatment could form Ga-N bonds at 19.48eV on the surface, which proved the weak formation of GaN when Ga₂O₃ treated with N₂O plasma. This is the reason for the decrease in turn-on voltage of the device. Subsequently, through the study of breakdown characteristics, it was found that both N₂O plasma treatment and O₂ plasma treatment can improve the breakdown characteristic of the diodes. It can be inferred that oxygen-containing plasma treatment effectively fills oxygen vacancies and reduces trap states in the anode region.

FIG. 3. XPS test result and reverse breakdown characteristic curves of the devices

      Finally, the trap state characteristics of the three devices were analyzed. The study showed that the devices treated with N₂O plasma and O₂ plasma exhibited smaller trap state energy levels and trap state densities. This demonstrated fully that oxygen-containing treatment can optimize interface properties and help to improve the performance of Ga₂O₃ based diodes.

FIG. 4. C-V characteristics and trap state information of devices

      This research results have been published in Applied Physics Letters with the title of "Research on the β-Ga₂O₃ Schottky barrier diodes with oxygen-containing plasma treatment". Yunlong He is the first author, Xuefeng Zheng and Xiaohua Ma are the corresponding authors. This research work provides an important foundation for the development of low turn-on voltage of Ga₂O₃-based power diodes.

Paper Link: https://doi.org/10.1063/5.0145659