The growing demand of the defense sector for high power applications that operate at high frequencies such as radio frequency (RF) power amplifiers opens a new window of opportunity for GaN as the base material for the devices to meet the early demand driven by radar, electronic warfare systems focused on providing ECM capabilities, specifically land based RF jammer designed for C-IED (Counter-Improvised Explosive Devices) applications to protect troops.
According to the research agencies, the demand from radar, EW and communications systems will fuel the military GaN RF market at a faster than average CAGR of 28 per cent, compared to 15 per cent for the commercial sector. The GaN RF military market will represent almost 60 per cent of the total GaN market in 2019 and will still be in a relatively early stage of deployment so the potential for growth will extend over many years to come.
The GaN technology outperforms other RF technologies because it can simultaneously offer the highest power, gain, and efficiency combination at a given frequency and because it operates at a higher operating voltage for a reduced system current. In this book, we fill you in on GaN semiconductors, the GaN field-effect transistor (GaN FET), and some practical considerations for deployment of GaN semiconductors.
GaN is a very hard material; its atoms are bonded by a very ionic gallium-nitrogen chemical bond that produces a bandgap of 3.4 electron volts (eV). The bandgap refers to the energy required to free the electron from its orbit around the nucleus and allow it to move freely through the solid. The bandgap is an important parameter that ultimately determines the mass of the freely moving electrons and the electric field that the solid is able to withstand. Hence, GaN is also sometimes referred as a wide bandgap semiconductor. In comparison, gallium arsenide (GaAs) has a bandgap of 1.4 eV and silicon (Si) has a bandgap of only 1.1 eV.
Further GaN-on-SiC approach combines the high power density capabilities of GaN with the superior thermal conductivity and low RF losses of SiC. That’s why GaN-on-SiC is the combination of choice for high power density RF performance compared to that of GaN-on-Si combination which exhibit a much poorer thermal performance and higher RF losses but is much cheaper. Hence, GaN-on-Si is the combination of choice for price-sensitive power electronics applications. Since GaN is a relatively a new technology compared to other semiconductors, such as Si and GaAs, it has become the technology of choice for high-RF, power-hungry applications like those required to transmit signals over long distances or at high-end power levels (such as radar, base transceiver stations [BTS], satellite communications, electronic warfare [EW], and so on).
GaN-on-SiC stands out in RF applications because of high breakdown field, high saturation velocity and outstanding thermal properties. Since GaN’s has a large bandgap, therefore it has a high breakdown field, which allows the GaN device to operate at much higher voltages than other semiconductor devices, therefore, making it ideal for higher-power applications. Also, the electrons on GaN have a high saturation velocity i.e. the velocity of electrons at very high electric fields. When combined with the large charge capability, implies that the GaN devices can deliver much higher current density. Since the RF power output is the product of the voltage and the current swings, so a higher voltage and current density can produce higher RF power in a practically sized transistor. Hence, GaN devices can produce much higher power density. Further GaN-on-SiC devices exhibit outstanding thermal properties, due largely to the high thermal conductivity of SiC, which means that GaN-on-SiC devices do not get as hot as GaAs or Si devices when dissipating the same power.
Companies like Cree, RFHIC, TriQuint, RFMD, Macom, Freescale, NXP, Raytheon and more are all making important contributions to improve capabilities in defense sector at the system level. From military communications to radar and sensing to electronic warfare, today’s battlefield systems require high performance, the utmost in reliability and affordability to provide war-fighters with the tools they deserve. Incorporating GaN in products will deliver quality performance for all harsh and unforgiving condition environments. Also, GaN is starting to underpin newer radar systems with high power capabilities across the wide range of frequencies used for radar systems seeing implementation of this technology across land based and shipborne radar systems, competing against both TWT-based and GaN based radar systems. The penetration of GaN will spread towards airborne systems moving forwards as well as use in space-based radars.