At the Fraunhofer Institute for Applied Solid State Physics IAF in Freiburg, Germany, research is being conducted into energy-efficient radio modules that enable greater bandwidth utilization and higher data transmission rates than previously used technologies.
The key to this is the semiconductor gallium nitride (GaN). It can be used to close the technology gap that exists between 5G and 6G.
High frequency technology with gallium nitride (GaN)
The semiconductor gallium nitride enables the production of energy-efficient miniaturized high-frequency electronics.
Gallium crystals look similar to aluminum and share some chemical properties with it.
High-performance Radio Module based on Gallium Nitride
Network expansion and the digitization of communications require innovative components that can outperform their predecessors. Radio modules, batteries, sensors and other electrotechnical components are therefore constantly being further developed. At the Fraunhofer Institute for Applied Solid State Physics IAF, research is being conducted into high-performance radio modules that can, on the one hand, form a new basis for 5G networks and, on the other, make 6G possible. The radio modules of Fraunhofer IAF are based on gallium nitride, which is processed on silicon wafers.
The Semiconductor Gallium Nitride
Gallium is a metal that is a waste product of metal production. It is silvery-white, can be easily liquefied (at below 30 °C) and is similar to aluminum in its chemical properties. In combination with nitrogen, gallium nitride is produced in a complex manufacturing process. It is a robust crystalline semiconductor that has been used for blue and green LEDs since the 1990s. It is sometimes referred to as 'the' semiconductor material of the future because gallium nitride chips allow current to pass much faster and with less dissipation compared to silicon chips.
As a component in rechargeable batteries, gallium nitride enables lower power dissipation than other semiconductors because less power is lost as heat. This makes gallium nitride an energy- efficient material that has the potential to save large amounts of energy in many applications. In a radio module, for example, it allows high switching frequencies. At the same time, the efficiency with which the supplied power is converted into microwave power is greatly increased compared to conventional silicon-based radio modules, enabling systems to be several orders of magnitude more compact.
Fraunhofer IAF has presented two variants of the radio module: the gallium nitride-on-silicon radio module and the gallium nitride-on-silicon carbide radio module. Silicon is a low-cost substrate material, which allows the radio module to be priced in a commercially appealing way. Silicon carbide, on the other hand, is used as the carrier for the higher-power version. It is more energy efficient while allowing better cooling than silicon. As a result, designs that are ten times smaller become possible. However, because silicon carbide is very expensive to produce – it takes 14 days and takes place at 2,500 °C – it is one of the most expensive semiconductor materials in the world. A 4-inch wafer costs around 1,000 US dollars.
Gallium Nitride f0r 6G
Sustainable use of resources and simultaneous technology development are only possible if energy-efficient materials such as gallium nitride are used.
Gallium nitride is helping to address the increasing energy demands of networks with more energy-efficient systems.
Gallium Nitride for Tomorrow's Radio Communications
Fraunhofer IAF's radio module reaches high frequencies relevant for 6G mobile communications up to 60 GHz while simultaneously enabling the use of an enormous bandwidth. At 56 to 63 GHz, it is possible to use 7 GHz of the absolute bandwidth with the gallium nitride-based radio module.
By comparison, 4G/LTE uses bands in the 450 to 2,600 MHz frequency range with a maximum absolute bandwidth of 30 MHz; 5G uses a bandwidth of 15 MHz in the 2.1 to 3.6 GHz range. A 7 GHz bandwidth allows enormously large amounts of data to be sent within a very short time.
Everyday Life with High Frequency Technology
The Internet of Things (IoT) and the Industrial IoT (IIoT) depend on high-performance radio modules. Maximum performance is currently achieved with the 5G standard on the frequency bands around 26, 28 and 39 GHz. Although this spectrum enables high data transmission rates, the radio waves have a short range due to their physical properties. This is why transmission towers are required at shorter distances from each other along with an increase in transmission power. The energy consumption of the communication systems is therefore very high and will continue to increase as the IoT grows.
“Towards Zero Power Electronics”
How can more powerful technology be developed when we need to use resources more sustainably and, in particular, save electricity?
The gallium nitride radio module was developed as an answer to this question. It was part of the Fraunhofer lead project "Towards Zero Power Electronics", with which the Fraunhofer-Gesellschaft pursued two complementary goals: To develop energy-saving electronics for the IoT and to make communication itself more energy-efficient. The gallium nitride radio module fulfills both goals. It enables high performance with low power consumption, while allowing efficiency gains in bandwidth utilization.
Currently, the efficiency of use in operation at 26 GHz is less than 10 %. This means that 90 % of the supplied energy cannot be used. The stated goal of "Towards Zero Power Electronics" was to achieve an efficiency of at least 30 %. The demonstrators developed as part of the project achieved this goal.
Greater Efficiency for 6G
The frequency bands between 71 and 84 GHz will play a major role for the 6G mobile communications standard. Currently, good broadband performance cannot be achieved in this range. Prof. Dr. Rüdiger Quay, Institute Director of Fraunhofer IAF, states: "6G will be able to offer incredible performance, however, it is already apparent that it has a very big efficiency problem."
Research into new high-frequency technologies is a key task to ensure that 6G not only enables new applications in the future through increased data transmission, but also conserves the increasingly valuable resource of electricity.
6G – World Record at Fraunhofer IAF
Batteries and Chargers
The higher switching capacities combined with low energy losses make gallium nitride an ideal material for power converters. These are an integral part of cell phones and are already often made of gallium nitride. The fact that chargers today are much smaller than they were ten years ago is also due to gallium nitride. The efficient flow of current in the semiconductor means that much less heat is generated, allowing components to be placed closer together without creating safety risks. The compact design generally requires less material, such as for the module's housing. This also makes a gallium nitride charger more resource-efficient in this respect.
Radio Sensor for Environmental Data
A sub-project of "Towards Zero Power Electronics" developed a low-energy Wake-Up RF Sensor Node that operates without a continuous power supply. The aim was to ensure that sensors that measure environmental variables such as particulate matter do not have to be in continuous operation, but can also be operated with low amounts of power, for example through energy harvesting, by making intelligent use of demand. To achieve the necessary efficiency for this, gallium nitride on silicon was used for the core module – the 'Core'. Other electronic devices can be connected to the core, which can be operated at very low energy.
The Wake-Up RF Sensor Node, for example, is activated with power in the micro-watt range and then read out.
Condition Monitoring of Industrial Machinery
Sensor nodes can collect data on the state of an industrial power system, such as a switchgear. Fraunhofer IISB has built a power converter for this purpose. The basic idea is that the sensor module is woken up with a data burst and read out completely. It then goes back into sleep mode. The state data shows if the system has become too warm at any point or even if it has been damaged. The readout with a burst is made possible by the gallium nitride radio module. This new form of monitoring, designed for IIoT and M2M communication, makes it possible to monitor the condition of systems in their history. System failures can thus be predicted and avoided.
6G – World Record at Fraunhofer IAF
6G is not yet feasible with existing technologies. "Gallium nitride is the key to achieving the efficiency and performance needed for 6G mobile communications," emphasizes Prof. Dr. Rüdiger Quay. This has been proven on an experimental radio link. Together with project partners, researchers from Fraunhofer IAF succeeded in achieving the world's first transmission performance of 100 Gbit/s over a freespace distance of 500 meters.
Gallium nitride enables the production of energy-efficient miniaturized devices that emit little heat.
Radio Node – The radio node with components made of gallium nitride allows environmental sensors to be operated in an extremely energy-efficient manner.
Mobile phone charger – As gallium nitride enables higher efficiencies, chargers with this semiconductor are smaller.
