With its rich portfolio of innovative solutions addressing the widest range of applications, NXP Semiconductors (NXP) is one of the main drivers of technological progress, constantly pushing the envelope. On September 29, NXP officially launched its state-of-the-art gallium nitride (GaN) fabrication plant (fab) extension within its Chandler-based factory in Arizona, unequivocally setting a course for the fast-growing 5G market. However, that does not mean the NXP is pulling its highly acclaimed LDMOS and SiGe (silicon-germanium) devices out of service. Instead, NXP’s strategy is to offer a full range of wireless infrastructure technologies and enrich its already diverse RF portfolio with highly optimized GaN-based solutions. Thus, in addition to their field-proven Si-based LDMOS and SiGe solutions, NXP is now able to offer highly optimized GaN RF power devices, laying the foundations for the mass deployment of 5G NR (New Radio) infrastructure.
The Most Advanced GaN Fab in the World
NXP is one of the largest LDMOS suppliers on the market. However, NXP experts believe that their LDMOS technology, while still superior in the applications it was intended for, has reached its maturity and that now is the right time to step out with the new RF GaN on SiC solutions that have been quietly developed in their labs for nearly 20 years. The inherent advantages of GaN technology over conventional silicon are numerous: GaN provides much higher efficiency and power density, can be operated at higher voltages (reducing the impedance matching complexity), and can deliver high power output at extremely high frequencies, over broad bandwidths. Finally, the thermal conductivity of the GaN on SiC compound is a magnitude better than that of the silicon, which greatly simplifies the cooling efforts. However, this promising technology had to overcome many obstacles before it could be released to mass production. NXP’s new RF GaN fab facilitates further development of this technology by providing greater control over production capacity and costs, as well as tighter integration between the process and device designers. Experts from NXP believe that their new fab sets the base for producing highly efficient GaN semiconductors that can be utilized even in the mm-wave range, offering significantly higher efficiency and power density than the existing solutions. The NXP’s new RF GaN fab in Chandler, Arizona, uses 6-inch (150 mm) wafers, making it the most advanced fab of its kind in the world.
GaN Technology Turns 5G into Reality
One of the hottest technological topics of today is certainly the topic of 5G communication. We are witnessing a growing number of solution providers in the market that offer the implementation of new 5G NR technology that promises many advantages over existing cellular network technologies: blazing-fast data transfer speeds, better coverage, greater network capacity, lower latency, and more. However, how to overcome the already quite advanced 4G LTE technology and the problems of physical propagation of high-frequency waves through space? The interface between mobile devices and cells in 5G NR technology relies on using massive Multiple-Input, Multiple-Output (mMIMO) phased-array antenna architectures to maximize the data rate between endpoints at scale. The phased array involves up to 64 independently powered antenna elements used to shape the RF signal in a process known as beamforming. However, an obvious question arises here: how to support so many RF Power Amplifiers (PAs) on a single tower and provide enough electricity without causing significant financial losses to mobile operators? Well, this is where GaN technology comes into play.
The sweet spot for 5G is currently within the range from 2.5 to 3.7 GHz, allowing up to 900 Mbps data rates, with each cell tower providing service up to several kilometers in radius. At the time of writing (2021), this level of service is the most widely adopted in many metropolitan areas. However, conventional LDMOS devices cannot operate quite efficiently at such high frequencies. On the other hand, NXP’s Airfast RF GaN on SiC devices offer much better performances and higher power densities. Combined with excellent thermal conductivity, NXP’s RF GaN devices provide high reliability, enabling a compact heatsink design, which is the key enabler for massive 64T64R MIMO radios while providing the highest level of integration required by the underlying infrastructure.
RF signals require highly linear amplification at the final stage to preserve the frequency and, more importantly, the amplitude content during transmission. However, the commonly used W-CDMA modulation scheme results in RF signals with a high crest factor (peak to average signal ratio), which are difficult to handle efficiently with just a single device. Therefore, final power stages are typically constructed as dual-channel Doherty PAs. On the other hand, early GaN on SiC technology suffered from serious linearity issues due to the so-called memory effect caused by the charge trapping, making it difficult to achieve linear performance. However, NXP’s latest GaN production technology effectively eliminated the charge trapping phenomenon through a refined fab process and redesigned device structure. As a result, their latest generation of GaN on SiC devices can benefit from using a much simpler linearization system design. In addition, Airfast RF power GaN devices feature extra ruggedness and can withstand extremely high output Voltage Standing Wave Ratios (VSWR) and broadband operating conditions.
RF GaN Power Transistors in Other Applications
In general, all high-power broadband applications operating at high frequencies can benefit from using RF GaN devices, as GaN is the best (and in some cases the only) technology that can meet all the requirements of such applications. One such example is the NXP’s Airfast A3G26D055NT4 dual RF power GaN transistor that can operate over a broad range of frequencies from 100 to 2690 MHz. This dual RF GaN transistor is designed for base station applications that require a very wide instantaneous bandwidth capability but can also be used in tactical wideband communication applications, thanks to the inherent robustness and high performance typical of NXP’s latest Airfast RF GaN series devices.
High-frequency electromagnetic waves (microwaves) are also widely used in many industries for rapid heat transfer. ISM (Industrial, Scientific, Medical)-band frequency of 2.45 GHz is the most used frequency, but some other frequencies in the ISM band can also be used. Microwave heating offers many advantages allowing selective heating, precise control of heating energy, compactness of the equipment, and the absence of combustion products. Microwaves are mostly used in the food industry for drying, pasteurization, cooking, blanching, and similar purposes, but they are also used in medicine for microwave ablation of cancerous tissue (frequencies of 2.45 GHz and 5.8 GHz). Until recently, a bulky electromechanical contraption called magnetron was the only solution for such applications. However, with the advent of GaN technology, solid-state industrial magnetrons started to appear on the market, bringing the whole spectrum of advantages, such as digital control, much lower harmonics content, the possibility to modulate the signal (Continuous Wave – CW or pulse), much lower operating voltage (kV vs. 50 V DC), improved ruggedness, longer lifecycle, and of course, much higher efficiency. NXP offers RF GaN HEMT solutions that can replace conventional industrial magnetrons, such as the MRF24G300H(S), a dual 300-W RF power GaN transistor, which operates across the range between 2400 and 2500 MHz, delivering power gain of 15.2 dB (typ. at 2450 MHz). This device also features an extremely high ruggedness and can withstand VSWR of more than 20:1 at all phase angles, with no degradation.
To simplify the design-in and accelerate a broader market adoption, NXP provides comprehensive support for their RF GaN devices in the form of datasheets, webinars, application notes, and an extensive set of reference boards and evaluation kits that simplify the design-in and enable faster time to market. The reference designs cover a broad range of frequencies and power ratings to support a variety of different RF applications. If you need further support, do not hesitate to reach out to EBV’s RF experts or your closest EBV Elektronik sales representative.
Si-based LDMOS devices continue to play a significant role in some niche applications that require very high RF power at narrow bandwidths of up to 4 GHz. In addition, their competitive prices ensure their existence in the market in the long run. However, as GaN technology matures, we will see more and more GaN devices in the broadest range of RF applications. And as we reap the final benefits of silicon-based technology, the most advanced GaN fabrication plants such as the NXP’s fab in Arizona allow us to open a new chapter in the history of semiconductors and fully explore of all the hidden potentials this innovative technology has to offer, making the world a better place.