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Description
The GaN is a representative wide band-gap compound semiconductor for efficient connectivity and energy systems in the future. The GaN is rapidly expanding in commercialization as a high-frequency HEMT using a 2DEG structure and a power-switching device having a high breakdown field. Among them, high-frequency power HEMT is applied to power amplifiers with wide-bandwidth characteristics and high output power density. There used in sub-6GHz RF front-end systems represented by 5G mobile telecommunication. In addition, expanding usage of PA MMIC in satellite communication applications and transmitter modules in military radar systems are using GaN HEMTs and MMICs.[1]
However, the GaN HEMT device should solve problems beyond the 5G system and ultra-high frequency applications, such as reduced output power due to current collapse, reduced drain efficiency, improving linearity, and short channel effect due to gate shrink. Epi-structure optimization is trying as one of the ways to solve these problems. Doping in the buffer layer[2], buffer-free structure[3], and GaN on GaN homo-epitaxy[4] are being developed to minimize the charge trapping effect and improve linearity. The thin barrier with high Al composition of AlGaN layer is developing to improve the short channel effect. A 150nm gate length process to cover up to 40GHz, minimizing an ohmic contact resistance[5], and inner source via structure is under development as a device process technology.
It is also researching the binding of diamond layers with GaN HEMT to improve heat dissipation concentrated in active areas. The GaN-on-diamond device is researched by directly deposing the diamond layer to the device structure and combining the diamond layer as a heat-spreader. The GaN-on-diamond device has the advantage of lowering the junction temperature by more than 30% under the same driving conditions and improving output power by more than 20%.
The microwave SSPA using GaN HEMTs can replace existing magnetron and vacuum tubes in various industrial, scientific, and medical fields. The GaN SSPA can output hundreds of W to 1 MW in the band from kHz to GHz. It has a reliable lifetime of more than 10 times that of conventional magnetron. The GaN SSPA can easily control the center frequency and uniform output by digital control. It has huge potential for various industrial applications such as high-temperature industrial heating applications, plasma sources for semiconductor equipment, and power sources for green hydrogen production.
References
[1] RF GaN Market and Technology 2021, Yole development
[2] D. S. Arteev et el. J. of Phys, Conference Seri. 1697 (2020) 012206
[3] D. Y. Chen et el. IEEE EDL, 41, 6 (2020)
[4] Yusuke et. al. IEEE BCICTS (2019)
[5] Niklas Rorsman, Chalmers Univ. of Tech.(2020)
| Keywords | GaN HEMTs, GaN power amplifier, GaN MMIC, GaN on GaN, GaN on Diamond, Microwave SSPA |
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