27 October 2022
Sumitomo Electric develops N-polar GaN HEMT using Hf-based gate dielectric
On 17 October at the 2022 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS) in Phoenix, AZ, USA, Japan’s Sumitomo Electric Industries Ltd (SEI) reported that it had developed a gallium nitride high-electron-mobility transistor (GaN HEMT) that uses N-polar GaN and, for the gate insulating layer, what is reckoned to be the world’s first hafnium (Hf)-based, highly heat-resistant, high-dielectric material, targeting the post-5G era, which will realize even greater capacity and high-speed communications.
In the future post-5G era, the transistors used in communication devices will be required to support higher power and higher frequencies for increased volume of data transmission.
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), which enables an inverted HEMT structure that increases the degree of freedom in device design and can reduce leakage current. 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 realization 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 says that it has hence used its years of experience in crystal growth technology to realize high-quality N-polar crystal without hillocks. In addition, by applying a type of hafnium-based highly heat-resistant and high-dielectric material (used in state-of-the-art silicon transistors) to the challenging gate insulating layer for the first time, the firm has created an N-polar crystal transistor incorporating a high-dielectric material and achieved what are said to be excellent high-frequency characteristics.
The newly developed N-polar GaN HEMT (using Hf-based gate dielectric) is a result of the ‘Research and Development Project for Strengthening Post-5G Telecommunication System Infrastructure’, commissioned by Japan’s New Energy and Industrial Technology Development Organization (NEDO).