Is GaN on Si the enabling technology that will also fuel next generation RF applications like 5G, IOT and displace the incumbent Si and GaAs technologies? You can certainly believe so as GaN on Si RF technology reached performance levels still out of reach a few years back.
The pillars of 5G
First trials of 5G are already taking place today. They are expected to reach 20Gbps peak data rates and a large number of users or sensing nodes for any given area. A high power efficiency (meaning less power required per transmitted bit), a latency of less than 1ms and ubiquitous connectivity are also on the list of promises of 5G. It will not only enhance existing telecom services drastically, but also enable emerging applications such as virtual reality, massive IoT (Internet of Things), and mission critical services.
So, what does all this new 5G architecture translate into for the RF technology of choice? It will need to support RF networks at less congested mmW frequency bands higher than today’s 6GHz and even up to the 100GHz range. Moreover, these new frequency bands also have a much higher useable bandwidth, which ideally should be covered with a single amplifier module. Furthermore, 5G will employ massive MIMO (multiple-in, multiple out) beamforming. This will require multiple transmit and receive chains for each antenna element in a phased-array configuration of the transceiver system. Compactness, low cost, high power density, linearity at mmW frequencies and integrability with CMOS technology are mandatory attributes for the power amplifier technology to meet objectives for both 5G infrastructure and handset architectures. Here GaN-on-Si technology comes to the stage. As a fundamentally superior RF semiconductor technology GaN is very well suited to achieve these demanding performance targets.
Higher performance levels
It has been demonstrated in the past that wide band gap GaN technology can perform at 10x the power density compared to GaAs and operates at higher voltages reducing impedance transformation challenges. It also exhibits higher efficiency, and shows excellent broadband operation at high frequencies. Additionally, GaN can operate at higher device operating temperatures, which in turn decrease cooling requirements and maintenance costs as well as improving reliability.
Wide band gap GaN technology performs at 10x the power density compared to GaAs.
An enabling RF technology
In the past years EpiGaN has achieved significant technological milestones that will help drive and adopt GaN on Si technology for the next evolution stage of cellular infrastructure technology – 5G. The company has developed and optimized a robust technology on resistive Si substrates up to 200mm diameter. This technology reduces RF signal loss on GaN-on-Si material to below 0.3dB/mm up to 20GHz. Even for future 5G frequencies in E-band up to 100GHz the RF signal loss stays well below 1 dB/mm.
EpiGaN has also partnered with Ommic, a leading European GaN foundry, and demonstrated the capability of their RF GaN on Si technology in a 100 nm gate-length open foundry MMIC process with a complete design kit. Compared to standard GaAs processes, the RF GaN on Si devices produced by this process have a far higher breakdown voltage: 40 V. Thanks to this, the output power density in the Ka-band is much higher, with a typical value of 3.3 W/mm and a peak of up to 5.7 W/mm. What’s more, the device features far greater robustness to input mismatch conditions.
Viable for smartphones
Last but not least: will RF GaN on Si technology win deployment in future smartphones? It works with relatively high voltages of 10 V or more today, so it is not the most suitable technology for handsets, which currently use between 3 V and 5 V. However with aggressive down-scaling of the device it could quickly become a viable candidate. As standards evolve, carrier aggregation is introduced to increase bandwidths, and there are ever increasing performance requirements for multi-mode, multi-band PAs.
Today GaN on Si technology is not the most suitable technology for handsets, but with aggressive down-scaling of the device it could quickly become a viable candidate.
RF GaN technology will come to the masses – no doubt about that – and it becomes more and more evident that with GaN on Si the dawn of a new RF technology has begun. Consequently, incumbent Si and GaAs will get dislodged to a large extent in next generation cellular 5G RF infrastructure applications.