RF power semiconductors for 5G shift to WBG materials

Advances in 5G technologies are driving new technical challenges in the semiconductor industry. 5G services work at higher frequencies to ensure higher transmission rates with very low latency. The use of new frequencies can create power efficiency problems, resulting in the need for new solutions.

5G is not merely a faster 4G mobile network. 5G is considered a “new” web, an infrastructure candidate for managing the internet of things. And it is fast. Networks running 5G will be up to 20× faster than the existing 4G network, enabling video download speeds up to 10× faster. High-performance power semiconductors and compound semiconductors such as gallium nitride (GaN), silicon carbide (SiC), and gallium arsenide (GaAs) are playing a key role in the 5G end-product development process.

5G and power consumption
With unprecedented complexity, the next 5G technology will revolutionize the industry in the coming years by making it totally intelligent. The challenges of such change are enormous: ultra-high bandwidth, latency up to 1 ms, and highly reliable connectivity. In addition, RF architectures need to be scalable, efficient, and extremely compact. 5G will require densification not only at the macro level with the installation of more base stations but also high power density at the device level.

To meet the needs of lower power consumption, smaller form factors, and better performance in terms of thermal management, RF power amplifiers based on GaAs, GaN, and SiC technologies started to set the pace during the advent of 4G. GaN is expected to become mainstream in the market for its improved power performance.

In addition, SiC devices offer lower costs and better performance than silicon (Si), and GaN-on-SiC can provide the best overall value. In particular, GaN-on-SiC offers 3× the thermal conductivity of GaN-on-Si.

Meanwhile, GaN and GaAs power semiconductors have more advantages over traditional Si-based semiconductors, such as higher switching speed, lower electrical current loss, and higher power density. Material suppliers are implementing new manufacturing solutions to offer lower costs and easier adoption. In particular, further progress is expected in the manufacturing process of GaN and GaAs compound semiconductors.

Spending on RF power semiconductors continues to grow, reaching nearly $2 billion in 2019, driven by 5G applications, according to ABI Research. The market analysis shows that the wireless infrastructure segment has experienced a significant turnaround, and all other segments are experiencing strong growth. LDMOS is playing an important role, but GaN continues its race to gain market share, solving the many technical challenges the market requires by bridging the gap with other much older, Si-based technologies.

The wireless infrastructure market accounts for about 75% of total sales and has performed exceptionally well, driven by 5G NR mid-band, according to ABI Research. The vertical market that shows the most vigorous growth in RF power semiconductor adoption outside of wireless infrastructure is commercial avionics and air traffic control.

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GaN and SiC power devices deliver big benefits to mil/aero systems

Compared to LDMOS, GaN-on-SiC offers significant improvements in 5G technology, such as superior thermal characteristics, and is more efficient for higher-frequency 5G applications.

5G use cases for smart cities (Image: Infineon Technologies)

Here is a sampling of RF power ICs suitable for 5G applications.

Analog Devices Inc.
Power amplifiers offered by Analog Devices Inc. (ADI) are based on GaN and GaAs semiconductor technology spanning kilohertz to 95 GHz. In addition to bare die and surface-mount components, the company’s portfolio also includes GaN-based power amplifier modules with output power exceeding 8 kW.

The ADPA7002CHIP is a GaAs, monolithic microwave integrated circuit (MMIC), pseudomorphic high-electron–mobility transistor (pHEMT), distributed power amplifier that operates from 20 GHz to 44 GHz. The amplifier provides 15 dB of small signal gain, 28-dBm output power at 1-dB gain compression (P1dB), and a typical output third-order intercept (IP3) of 40 dBm.

Functional diagram of the ADPA7002CHIP (Image: Analog Devices Inc.)

Infineon Technologies AG
Infineon Technologies provides GaN-on-SiC and GaN-on-Si RF power technologies for integrated architectures above 6 GHz and LDMOS for high-robustness systems below 6 GHz. Packaging innovations enable Doherty-integrated broadband amplifiers.

Flexible RF solutions for mobile and low-power infrastructure, including SiGe, BiCMOS, GaN mmWave, and CMOS RF technologies, meet optimal performance requirements with alternative options from cost-optimized to high-integration designs.

As the CPU’s current requirements increase to enable next-generation artificial intelligence and 5G grid workloads, DC/DC voltage regulators must provide more than 500 A to the load. With a true 16-phase PWM digital algorithm, the XDPE132G5C controller meets these high-phase-count requirements.

State-of-the-art ASICs and FPGAs in communication systems require V_OUT control with steps of less than 1 mV. This is inherent in the XDPE132G5C, which offers fine V_OUT control in 0.625-mV increments. Moreover, this solution supports the auto-restart requirements with options to reduce remote site maintenance due to power problems.

NXP Semiconductors
NXP Semiconductors offers a wide selection of RF power devices, including GaN, LDMOS, SiGe, and GaAs technologies. An example is the MMRF5014H, a 125-W continuous-wave (CW) RF power transistor optimized for wideband operation up to 2,700 MHz, which also includes input matching for extended bandwidth performance. With its high gain and high ruggedness, the device is well suited for CW, pulse, and wideband RF applications. Built with advanced GaN-on-SiC technology, the device is suitable for military and commercial applications, including narrowband and multi-octave wideband amplifiers, radar, jammers, and EMC testing.

The LDMOS power amplifiers are designed for TDD and FDD LTE systems. The AFSC5G23D37 is a fully integrated Doherty power amplifier module designed for wireless infrastructure applications that demand high performance in the smallest footprint. Target applications include massive MIMO systems, small outdoor cells, and low-power remote radio heads.

As the cellular market moves to higher frequency and higher power levels, GaN technology provides state-of-the-art linearizability and RF performance to simplify 5G deployments. The solutions also simplify massive MIMO implementations by enabling smaller, lighter active antenna systems, and multi-chip modules (MCMs) for a high level of integration.

The A2G35S160-01SR3 is a 32-W RF power GaN transistor for cellular base station applications covering the frequency range of 3,400 to 3,600 MHz. It provides high terminal impedances for optimal broadband performance, and it is designed for digital predistortion error correction systems and optimized for Doherty applications.

Macom
Macom offers a broad range of RF power semiconductor products as discrete devices, modules, and pallets designed to operate from DC to 6 GHz. The MAGB-101822-380A0P is a GaN HEMT D-mode amplifier pair designed for digital predistortion error correction systems and asymmetrical Doherty base station applications with 55-W average power. This device, in a plastic package, is optimized for cellular base station applications with high terminal impedances for broadband performance.

Qorvo Inc.
Qorvo Inc. offers highly integrated components and modules for the entire 5G infrastructure. GaN technology is used to build solid-state microwave power amplifiers (SSPAs). It benefits from a high fault voltage leading to a high power density. GaN power amplifiers can be built using a variety of implementation options.

PRFI Ltd. has implemented a Qorvo solution, the TGF2977, to design a 5-W X-band GaN power amplifier. The amplifier is optimized for the 9.3- to 9.5-GHz band, offers a small signal gain of 11 dB, and provides more than 37 dBm of output power at 3-dB gain compression with a corresponding drain efficiency of over 55%.

The TGF2977 is a 5-W (P3dB) wideband unmatched discrete GaN-on-SiC HEMT, which operates from DC to 12 GHz and a 32-V supply rail. The device is housed in an industry-standard 3 × 3-mm QFN package and is well suited to military and civilian radar, land mobile and military radio communications, avionics, and test instrumentation. The device can support pulsed and linear operations.

The TGA2219 is a 25-W GaN power amplifier offered as a high-power MMIC amplifier designed for commercial and military radar (Ku-band included) and satellite communication systems. Developed using TriQuint’s production 0.15-µm GaN-on-SiC process, the TGA2219 amplifier operates from 13.4 GHz to 16.5 GHz and provides 25 W of saturated output power with 27 dB of large signal gain and greater than 28% power-added efficiency (PAE). The TGA2219 is fully matched to 50 Ω with integrated DC blocking capacitors on RF ports to simplify system integration.

Wolfspeed, a Cree company
GaN-on-SiC has emerged as the frontrunner to take on all of the challenges and requirements brought about by the introduction of 5G networks. Wolfspeed’s portfolio focuses mainly on GaN-on-SiC HEMT. One example is the GTRA384802FC. This solution is a 400-W (P3dB) HEMT for use in multi-standard cellular power amplifier applications.

The HEMT features input and output matching, high efficiency, and a thermally enhanced package with earless flange. The device offers an efficiency of 62% and a 12-dB gain and can handle 10:1 VSWR @ 48-V, 63-W (WCDMA) output power. Its asymmetrical Doherty design guarantees main P3dB 200 W typical and peak P3dB 280 W typical.

Conclusion
Technology is evolving considerably. GaN is more efficient than silicon for 5G and has been the apparent heir of silicon in 5G power amplifiers for years. Thanks to developments in wafer and cost reduction, it is definitely catching on, especially when it comes to 5G mmWave networks.

GaN devices are replacing LDMOS devices in the market, especially in 5G telecommunications base stations, radar, and avionics, as well as other broadband applications. In future network designs, GaN and other wide-bandgap (WBG) materials will usurp existing LDMOS devices due to their physical properties. However, LDMOS will still hold a solid market share, owing to its maturity and low cost.