OKI and NTT Innovative Devices Corporation, led by President & CEO Hidehiro Tsukano, have developed a technology for mass-producing high-power terahertz devices. This advancement uses Crystal Film Bonding (CFB) technology. It allows bonding different materials, like indium phosphide (InP) uni-traveling carrier photodiodes (UTC-PDs), to silicon carbide (SiC). SiC is great because it dissipates heat well. The new approach boosts bonding yields and prepares for future commercial production. The companies plan to start this in fiscal year 2026.
Terahertz waves sit between radio waves and visible light in the electromagnetic spectrum. They blend the deep penetration of radio waves with the precise directionality of light. They are non-invasive, making them great for safety-critical uses. This includes non-destructive inspections and security screenings. Traditional X-ray tech cannot match this advantage. In the realm of wireless communication, terahertz waves are key to achieving higher data throughput. Their strong atmospheric attenuation is a challenge. It requires high-power devices and dependable mass production methods.
NTT Innovative Devices is improving UTC-photomixers to overcome challenges. They focus on output power and spectral features. For wireless applications, it’s important to achieve high output power at the 1dB compression point. This is especially true for standard multilevel modulation schemes. The team worked with a Japanese university to create a bonding method. This method directly integrates InP-based UTC-PDs onto SiC substrates. It uses SiC’s excellent thermal conductivity. This innovation has resulted in photomixer devices that now exceed 1 mW in output power at the 1 dB compression point. That’s about ten times better than older devices.
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Traditional wafer bonding can be tough for mass production. Large bonding areas mean even small defects can lead to big problems. Also, material efficiency matters. Conventional methods rely on just a small part of the costly InP material.
To tackle these issues, OKI used its CFB technology. This tech, honed over 20 years in the printer industry, splits InP-based crystal films at the device level. Only the needed parts bond to the SiC wafer. This boosts bonding yields and improves material efficiency. The process allows wafer-scale bonding. This boosts the bonding yield from about 50% to nearly 100%. It also cuts down on material waste and lessens environmental impact.
NTT Innovative Devices developed UTC-PD chips on SiC substrates. They used bonded crystal films for this process. Testing showed these devices produced more than 1 mW of output power at the 1dB compression point. They also maintained great linearity. The dark current dropped to about one-third of that seen in traditional bonding methods. This shows that the new technique keeps the properties of InP-based films intact during bonding.
This teamwork is a big step in making high-power terahertz technology more practical for real-world use.
今後に向けて オーキー そして NTT Innovative Devices Corporation plan to begin mass production in FY2026. They plan to work closely with industry and academic partners. This will help speed up the deployment of 6G communication technologies. It will also expand the use of non-destructive sensing applications. These efforts help build a next-generation society. They also promote Japan’s leadership in advanced device technology worldwide.
