A research group led by Professor Makoto Kasu at Saga University has made a groundbreaking achievement in the development of power circuits using diamond semiconductors. In a world-first, the group has successfully demonstrated high-speed switching operation of less than 10 nanoseconds. This breakthrough is expected to be applied to Beyond 5G and communication satellites.
As the capacity of communication increases, there is a growing demand for high-frequency and high-output semiconductor devices. While mobile terminals have a frequency and output of around 1.5 GHz/1W, communication satellites and television broadcasting stations require 10 GHz/1 kW or more, and Beyond 5G requires 100 GHz/100W or more. Vacuum tubes are currently used for these areas, but they have lower efficiency and larger energy losses compared to semiconductors, making semiconductorization strongly desired.
Diamond semiconductors have properties that significantly exceed existing materials, making them ideal for high-frequency power devices. In 2022, Professor Kasu achieved the world's highest output power of 875 MW/cm2 and output voltage of 3659 V as a diamond semiconductor device. However, it has been reported that the deterioration of the device occurs quickly when a diamond semiconductor is operated as a power circuit, making long-term operation difficult and practical use not easy.
To overcome this issue, the research group developed a power circuit using a unique method of wire bonding with gold wires between the diamond semiconductor and the printed circuit board. The operation of this circuit was confirmed to show ultra-high-speed switching operation of less than 10 nanoseconds and a significant reduction in loss. Moreover, no deterioration of the characteristics was observed even after continuous measurement for 190 hours.
This breakthrough opens up the way to expand the application of diamond semiconductors to communication purposes such as Beyond 5G and power control devices for electric vehicles. The research group aims to elucidate the mechanism of characteristic changes of the developed circuit and develop devices with countermeasures. Moreover, they will accelerate research and development towards practical use by conducting operation at even higher voltages and dynamic characteristic tests.