NTT has achieved a global first by demonstrating high-frequency signal amplification in aluminum nitride (AlN)–based transistors, marking a major milestone for post-5G wireless technology. By solving long-standing problems of high contact resistance and high channel resistance, NTT engineered a new AlGaN contact layer and a polarization-doped channel structure that enable low-resistance operation even at high aluminum compositions above 75 percent.

Using these innovations, NTT’s prototype transistors delivered strong drain current, excellent current linearity, and high on/off ratios. The device with 85 percent Al composition reached a maximum oscillation frequency of 79 GHz, proving millimeter-wave capability and setting a performance record for AlN-based transistors. The breakthrough signals AlN’s potential to expand beyond next-generation power devices into high-frequency wireless applications, enabling wider coverage and faster speeds in the post-5G era. The results will be presented at the IEEE International Electron Devices Meeting (IEDM 2025).