The amount of energy saved worldwide through the use of LEDs for general lighting is estimated to be 952.5 TWh/year, which is comparable to the total electricity generation in Japan (1043.6 TWh/year, 2016). Also, nitrides are thought to be semiconducting material systems that can be used in high-power microwave, millimeter-wave and THz devices in next-generation 5G and post-5G wireless communication systems. The energy loss of all-electric power circuits such as inverters and converters can be reduced to one-tenth by replacing Si-based MOSFETs and IGBTs with GaN-based transistors and diodes. In the future, the mobility of humans will be increasingly dependent on vehicles driven by electricity. Electric vehicles (EVs) are one of the most important items for establishing a sustainable society. One of the problems of EVs is their short driving range owing to the insufficient capacity of the battery. Another is their long charging time. We can reduce the electricity consumption of inverters in EVs by 65% by replacing conventional IGBTs with GaN-based high-power HEMTs. In our newly developed EVs, IGBTs will be replaced with GaN-based power devices not only in the inverter but also in all the DC－DC converters. GaN-based systems will also be used in all the displays inside the car, and the headlights will be composed of GaN-based high-brightness LEDs/LDs lamps. Thus, we call such a vehicle, “All GaN vehicle”.
AlGaN-based UV-C LDs may replace conventional solid-state lasers with a fourth-harmonic generation system. In 2019, our group successfully fabricated a 271.8 nm LD on an AlN substrate. To realize current injection lasing, several issues should be overcome. One of the most serious issues is the low hole concentration in the P-type AlGaN cladding layer. From blue LDs to UV LDs, the threshold current density increases drastically with shortening the emission wavelength. We realized efficient hole injection, thus reducing the threshold current density, by using a polarization doping structure. Optimization of the active layer will lead to high-power operation, thus realizing efficient direct diode lasers for future low-carbon-emission laser processing.
We are presently developing an open innovation platform to realize such novel power and opto-electronic devices and systems. We have established the Center for Integrated Research of Future Electronics (CIRFE). The purpose of CIRFE is to gather specialists in different fields such as those in the crystal growth of GaN, AlN, SiC, and carbon nanotubes, device fabrication and characterization, simulation, circuit design, module design, and system applications, thus contributing to realizing a carbon neutral society.