Gallium nitride (GaN) based semiconductors have been commercially available for several years at this point. GaN technology has made extensive inroads into many power electronics applications, and increasingly in RF/microwave/millimetre-wave applications.
GaN, as a semiconductor, has high electron mobility, high band-gap voltage, is very rugged, and can be realised in a variety of technologies using layering and epitaxial growth (semiconductor on insulator technology). This includes GaN on silicon carbide (GaN-on-SiC), GaN on silicon (GaN-on-Si), GaN-on-GaN, and even GaN on diamond. The various insulative substrates exhibit a range of performance, reliability, power density, price, and other manufacturing/design concerns. This allows for GaN technology to meet the needs for a vast range of applications.
The most common applications for GaN to date in the RF industry have been for power amplifiers (PA). However, several companies have also developed GaN low-noise amplifiers, mixers, diodes, switches, resistors, and other RF components.
The prevailing theme is that GaN devices tend to be designed for high-frequency and high-power use cases. This is a result of GaN’s cost being a premium over other high-frequency semiconductor technologies, such as Si and gallium arsenide (GaAs), but with far better high-power performance. For instance, in some high-frequency, wide-bandwidth, and high-power applications beyond 6 GHz, several GaAs or Si PAs would be needed to reach the performance of a single GaN PA that may also be more reliable and efficient. In other cases, GaN has also replaced GaAs and indium phosphide (InP) devices in high-frequency and wideband applications, such as sensing and test and measurement instruments.
These features have also led to GaN devices penetrating markets typically dominated by legacy technologies, such as laterally diffused metal oxide semiconductor (LDMOS) Si PAs and travelling wave tube amplifiers (TWTAs). These applications include high-frequency and high-peak pulsed power use cases, such as radar, radar jammers, and satellite communications in the Ka band (27 GHz to 40 GHz). Due to the versatility of GaN devices, GaN amplifiers are also used in commercial wireless applications, such as the ongoing rollout of 4G/5G sub-6 GHz and 5G millimetre-wave infrastructure.
GaN amplifiers and other devices are made to handle frequencies from near DC to tens of gigahertz. Recent research has also explored GaN devices that operate to over 100 GHz and even terahertz (THz). As most mainstream applications are still below 6 GHz, the largest markets for GaN devices are replacing high-power amplifiers (HPAs) in these frequencies. Defence, aerospace, and satellite communications and sensing applications are also embracing millimetre-wave GaN PAs at a high rate.
Due to this diversity of use cases it is difficult to accurately predict the market growth and penetration of GaN technology, but market research firms generally forecast GaN’s growth at more than 10% compound annual growth rate per year through the 2020s.
Other challenges for predicting the growth and penetration of GaN technology in certain markets also come from the extent of the research and development being invested in GaN. A main area of this research is developing GaN PAs with high power added efficiency (PAE) for modern wireless communications. The new modulation schemes and techniques employed by new 5G and other wireless communication technologies incur additional design constraints for PAs, such as the need for high efficiency, high power, and wide bandwidth.
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