Why GaN?

Why GaN?

I was fortunate in my time at the Sensors Directorate of the Air Force Research Laboratory to watch Gallium Nitride (GaN) evolve from a laboratory curiosity to the dominant Radio Frequency (RF) technology for RADAR, Comm, and Electronic Warfare (EW) applications. My first work with GaN was on tiny slivers of material more precious than gold due to their scarcity, however, now you can get devices or circuits fabricated at multiple foundries on 6” (and even 8”) wafers. All of that is great, but you may be asking yourself “why GaN?”

Gallium Nitride (GaN) has increasingly been recognized as a vital material for RF applications due to its unique properties that enhance performance in high-frequency and high-power environments. Here are several key reasons why GaN is particularly useful for RF applications:

  1. High Electron Mobility: GaN exhibits high electron mobility, which allows for faster switching speeds compared to traditional semiconductor materials like silicon or Gallium Arsenide (GaAs). This characteristic is crucial for RF applications where rapid signal processing is required.

Glen “David” Via
Director of Programs

  1. Wide Bandgap: The wide bandgap of GaN (approximately 3.4 eV) enables devices to operate at higher voltages and temperatures without compromising performance. This property makes GaN suitable for high-power RF amplifiers and transmitters, which are essential in telecommunications and radar systems.
  2. High Power Density: GaN devices can handle higher power levels in a smaller footprint than their silicon and GaAs counterparts. This capability allows for more compact designs in RF systems, making them ideal for applications such as mobile communications, satellite communications, and military radar systems.
  3. Thermal Management: GaN has superior thermal conductivity compared to other semiconductor materials, which helps dissipate heat more effectively during operation. This feature enhances the reliability and longevity of RF devices operating under demanding conditions.
  4. Efficiency: Devices made from GaN can achieve higher efficiency levels, reducing energy consumption and heat generation during operation. For instance, low noise amplifiers (LNAs) utilizing GaN technology can provide significant improvements in signal integrity while managing output power effectively.
  5. High Linearity: GaN devices exhibit excellent linearity characteristics, which are critical for maintaining signal fidelity in RF applications like amplifiers and switches. High linearity reduces distortion in transmitted signals, ensuring clearer communication.
  6. Versatility Across Applications: The performance advantages of GaN are important for military applications but also extends across various dual use and commercial sectors including telecommunications (for 5G networks), automotive (for advanced driver-assistance systems), aerospace (for satellite communications), and renewable energy systems (inverters).

Figure 1. graphically shows GaN functional properties relative to GaAs and Si for several key performance parameters enabled by the materials properties inherent in GaN. The combination of increased available drain current and high breakdown field results in a 5x – 10x increase in RF power over competing technologies. Excellent switching speed or maximum oscillation frequency combined with the high breakdown field improves overall device efficiency and produces a high gain bandwidth product. Add maximum operating temperatures and the result is a more robust technology that can operate in harsh conditions with increased reliability. The combination of these performance advantages can greatly size, weight, and power (SWAP) for a system application.

Figure 1. Radar chart showing the relative performance of GaN, GaAs, and Si
for several critical operational parameters.

Now that you can see why GaN offers such great performance you may be asking yourself how to take advantage of it. MMEC and CA DREAMS recently launched a GaN Prototype Accelerator (GaNPA) Multi-Project Wafer (MPW) Opportunity to enable access to state-of-the-art (SOTA) GaN technology. The objective of the GaNPA is to lower barriers to entry to advanced GaN, to engage with non-traditional GaN power amplifier designers, foster domestic design and fabrication capability, and enable rigorous RF design practices. The GaNPA MPW Opportunity is offering access to die area on Northrop Grumman Microelectronics Center’s GaN15 technology, design services through CA DREAMS MOSIS 2.0, and EDA tool access along with cloud compute resources through MMEC’s DESIGN Hub. MMEC is also offering RF characterization support of fabricated circuits.
Figure 2. shows the timeline for the initial GaNPA Opportunity. Of the white papers received eleven design teams and twelve circuit concepts were selected for inclusion on the GaNPA MPW. Selected design teams are a mix of academic groups and small businesses. The academic groups are Michigan State University (MSU), Ohio State University (OSU), University of Illinois Urbana Champaign (UIUC), University of Texas Dallas (UTD), and the University of Vermont (UVM). Smal businesses include DOES, Fresnel, NxBeam, ReconRF, and OSEMI.
White paper selection was based on the technical merit of the circuit design concept, the application or application area being targeted, and how the proposed design concept will provide novel or unique solution enabled by advanced GaN technology offering and/or innovative design approach. Performance metrics needed to be identified describing the limits of current solutions and how the proposed circuit concept improves on SOTA. The white paper also needed to include a discussion of prior experience with circuit design, EDA tool use, GaN technology, and RF testing.

Figure 2. Timeline for GaNPA MPW Opportunity

More information on the GaNPA Opportunity can be found at https://ganchallenge.com.