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GaN On Silicon Primed For RF Power


Can GaN-on-silicon move on from just serving 600 V and below power management systems, wireless charging and LIDAR, to win deployment in next-generation RF applications, such as 5G and the Internet of Things? By Markus Behet and Joff Derluyn from EpiGaN

For several decades, innovations in electronics have tended to draw on silicon and GaAs-based technologies, devices and integrated circuits. Take cellular infrastructure: its increases in complexity from 2G to 4G-LTE have been underpinned by continuous improvements in GaAs HEMTs, HBTs and silicon LDMOS devices.

One downside of all these incumbent semiconductor technologies is that they are now encroaching their theoretical limits. Consequently, any improvement at the system level requires a huge effort by design engineers, and draws on ever increasing developments costs. Given this state of affairs, there is an urgent need for a new RF semiconductor technology to step in and fulfil the promises of 5G RF systems "“ and it is here that GaN technology comes to the stage.

Wideband GaN technology is definitely not a newbie to the semiconductor market. It is already being deployed in the likes of power supplies and motor drives, which are benefitting from highly efficient 600 V GaN-on-silicon HEMTs. In addition, there are GaN-on-SiC RF products that are being used in base stations, Satcom, military and CATV systems. Due to all this activity, on both of these formats of GaN, the total addressable market in 2017 was worth $400 million.

Another opportunity for revenue growth will come with the dawn of the next generation of cellular infrastructure "“ 5G. Initial deployments, which will take place by 2020, promise to lead to: peak data rates of 20 Gbit/s; a large number of users or sensing nodes for any given area; a high power efficiency, enabling less power per transmitted bit; a latency of less than 1 ms; and ubiquitous connectivity. This revolution will not only enhance existing telecom services drastically, but enable emerging applications, such as virtual/augmented reality, autonomous cars, massive IoT, and mission critical services.

These changes have led market analysts ABI to argue that 5G should be viewed as a general purpose technology that will act as a catalyst for transformative changes of work processes, and will establish a new set of rules of competitive economic advantages. The impact will be so great, says ABI, that by 2035 it will trigger a global economic output of $12.3 trillion "“ that's comparable to current levels of annual US consumer spending.

Figure 1. EpiGaN's optimized RF GaN-on-silicon HEMT structure produces very low RF losses, according to measurements on transmission line structures.

The pillars of 5G

To meet stringent user requirements, workgroups defining the 5G roadmap have devised a novel architecture for the 5G network. One of its three key features is the use of many small network cells, known as pico- and femto-cells. They will allow a high user density and low latency. Another key ingredient in 5G systems is the use of transceivers that operate at a higher baseband frequency and have a very large (analogue) bandwidth that can meet digital bandwidth requirements. The third important innovation associated with the introduction of 5G is the move from omni-directional broadcasting to the use of directional beams for each connection. This will enhance energy efficiency, and enable more efficient use of the RF spectrum.