Sumitomo Electric develops 'post-5G' GaN-HEMT
Device uses N-polar GaN and hafnium for the gate insulating layer
Sumitomo Electric has developed a GaN-HEMT that uses N-polar GaN and, for the gate insulating layer, the world's first hafnium (Hf)-based, highly heat-resistant, high-dielectric material, setting its sights on the post-5G era, which will realise even greater capacity and high-speed communications.
Conventionally, Ga-polar (0001 orientation) GaN has been widely used. Along with the demand for further higher power and higher frequencies, however, attention is being focused on the improvement of characteristics with N-polarity (000-1 orientation) (the crystal orientation is different from that of the Ga-polarity), which enables an inverted HEMT structure that increases the degree of freedom in device design and can reduce leakage current (pictured above).
Meanwhile, N-polar crystals have the problem of being prone to irregularities caused by abnormal growth called hillocks. In addition, in terms of device design, the realisation of an inverted HEMT structure required the development of a high-quality gate insulating layer that would serve as a barrier against the gate electrode in place of the conventional semiconductor barrier layer.
Sumitomo Electric has made high-quality N-polar crystals without hillocks (see picture above). In addition, by applying a type of Hf-based highly heat-resistant and high-dielectric material, used in state-of-the-art siliconi transistors, to the challenging gate insulating layer for the first time, the company completed an N-polar crystal transistor incorporating a high-dielectric material and achieved excellent high-frequency characteristics.
This achievement is the result of the 'Research and Development Project for Strengthening Post-5G Telecommunication System Infrastructure' commissioned by the New Energy and Industrial Technology Development Organisation (NEDO). The details were announced on October 17, 2022 (local time) at the 2022 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS) held in Phoenix, US