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Gallium nitride ( ) is a binary Boron group/Nitrogen group direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 electronvolt affords it special properties for applications in optoelectronic, high-power and high-frequency devices. For example, GaN is the substrate that makes violet (405 nm) laser diodes possible, without requiring nonlinear optical frequency doubling.
Its sensitivity to ionizing radiation is low (like other Boron group ), making it a suitable material for solar cell arrays for . Military and space applications could also benefit as devices have shown stability in high-radiation environments.
Because GaN transistors can operate at much higher temperatures and work at much higher voltages than gallium arsenide (GaAs) transistors, they make ideal power Amplifier at microwave frequencies. In addition, GaN offers promising characteristics for THz devices. Due to high power density and voltage breakdown limits GaN is also emerging as a promising candidate for 5G cellular base station applications. Since the early 2020s, GaN power transistors have come into increasing use in Power supply in electronic equipment, converting AC mains electricity to low-voltage Direct current.
The U.S. Army Research Laboratory (ARL) provided the first measurement of the high field electron velocity in GaN in 1999. Scientists at ARL experimentally obtained a peak Steady state velocity of , with a Transient state time of 2.5 picoseconds, attained at an electric field of 225 kV/cm. With this information, the electron mobility was calculated, thus providing data for the design of GaN devices.
An early synthesis of gallium nitride was by Robert Juza and Harry Hahn in 1938.
GaN with a high crystalline quality can be obtained by depositing a buffer layer at low temperatures. Such high-quality GaN led to the discovery of p-type GaN, p–n junction blue/UV- and room-temperature stimulated emission (essential for laser action). This has led to the commercialization of high-performance blue LEDs and long-lifetime violet laser diodes, and to the development of nitride-based devices such as UV detectors and high-speed field-effect transistors.
In 2010, the first enhancement-mode GaN transistors became generally available. Only n-channel transistors were available. These devices were designed to replace power MOSFETs in applications where switching speed or power conversion efficiency is critical. These transistors are built by growing a thin layer of GaN on top of a standard silicon wafer, often referred to as GaN-on-Si by manufacturers. This allows the FETs to maintain costs similar to silicon power MOSFETs but with the superior electrical performance of GaN, and consists of growing GaN on silicon wafers using MOCVD Epitaxy. Another seemingly viable solution for realizing enhancement-mode GaN-channel HFETs is to employ a lattice-matched quaternary AlInGaN layer of acceptably low spontaneous polarization mismatch to GaN.
GaN power ICs monolithically integrate a GaN FET, GaN-based drive circuitry and circuit protection into a single surface-mount device. Integration means that the gate-drive loop has essentially zero impedance, which further improves efficiency by virtually eliminating FET turn-off losses. Academic studies into creating low-voltage GaN power ICs began at the Hong Kong University of Science and Technology (HKUST) and the first devices were demonstrated in 2015. Commercial GaN power IC production began in 2018.
GaN high-electron-mobility transistors (HEMT) have been offered commercially since 2006, and have found immediate use in various wireless infrastructure applications due to their high efficiency and high voltage operation. A second generation of devices with shorter gate lengths will address higher-frequency telecom and aerospace applications.2010 IEEE Intl. Symposium, Technical Abstract Book, Session TH3D, pp. 164–165
GaN-based metal–oxide–semiconductor field-effect transistors (MOSFET) and metal–semiconductor field-effect transistors (MESFET) also offer advantages including lower loss in high power electronics, especially in automotive and electric car applications. Since 2008 these can be formed on a silicon substrate. High-voltage (800 V) Schottky barrier diodes (SBDs) have also been made.
The higher efficiency and high power density of integrated GaN power ICs allows them to reduce the size, weight and component count of applications including mobile and laptop chargers, consumer electronics, computing equipment and electric vehicles.
GaN-based electronics (not pure GaN) have the potential to drastically cut energy consumption, not only in consumer applications but even for power transmission public utility.
Unlike silicon transistors that switch off due to power surges, GaN transistors are typically depletion mode devices (i.e. on / resistive when the gate-source voltage is zero). Several methods have been proposed to reach normally-off (or E-mode) operation, which is necessary for use in power electronics:
Thales Group introduced the Ground Master 400 radar in 2010 utilizing GaN technology. In 2021 Thales put in operation more than 50,000 GaN Transmitters on radar systems.
The U.S. Army funded Lockheed Martin to incorporate GaN active-device technology into the AN/TPQ-53 radar system to replace two medium-range radar systems, the AN/TPQ-36 and the AN/TPQ-37. The AN/TPQ-53 radar system was designed to detect, classify, track, and locate enemy indirect fire systems, as well as unmanned aerial systems. The AN/TPQ-53 radar system provided enhanced performance, greater mobility, increased reliability and supportability, lower life-cycle cost, and reduced crew size compared to the AN/TPQ-36 and the AN/TPQ-37 systems.
Lockheed Martin fielded other tactical operational radars with GaN technology in 2018, including TPS-77 Multi Role Radar System deployed to Latvia and Romania. In 2019, Lockheed Martin's partner Elta Systems, developed a GaN-based ELM-2084 Multi Mission Radar that was able to detect and track air craft and ballistic targets, while providing fire control guidance for missile interception or air defense artillery.
On April 8, 2020, Saab AB flight tested its new GaN designed AESA X band radar in a JAS-39 Gripen fighter. Saab already offers products with GaN based radars, like the Giraffe radar, Erieye, GlobalEye, and Arexis EW. Saab also delivers major subsystems, assemblies and software for the AN/TPS-80 (G/ATOR)
India's Defence Research and Development Organisation is developing Virupaakhsha radar for Sukhoi Su-30MKI based on GaN technology. The radar is a further development of Uttam AESA Radar for use on HAL Tejas which employs Gallium arsenide technology.
Turkish Aselsan company delivered the first GaN-based Turkish AESA radar, ALP 300-G, to the Turkish Armed Forces in May 2024.
Gallium nitride can also be synthesized by injecting ammonia gas into molten gallium at at normal atmospheric pressure.
Bulk GaN is non-toxic and biocompatible.Shipman, Matt and Ivanisevic, Albena (24 October 2011). "Research Finds Gallium Nitride is Non-Toxic, Biocompatible – Holds Promise For Biomedical Implants". North Carolina State University Therefore, it may be used in the electrodes and electronics of implants in living organisms.
CMOS logic
In 2016 the first GaN CMOS logic using PMOS and NMOS transistors was reported with gate lengths of 0.5 μm (gate widths of the PMOS and NMOS transistors were 500 μm and 50 μm, respectively).
Applications
LEDs and lasers
GaN-based violet are used to read . The mixture of GaN with indium (InGaN) or Aluminium (AlGaN) with a band gap dependent on the ratio of In or Al to GaN allows the manufacture of light-emitting diodes () with colors that can go from red to ultra-violet.
Transistors and power ICs
GaN transistors are suitable for high frequency, high voltage, high temperature and high-efficiency applications. GaN is efficient at transferring current, and this ultimately means that less energy is lost to heat.
Radars
GaN technology is also utilized in military electronics such as active electronically scanned array radars. "Gallium Nitride-Based Modules Set New 180-Day Standard For High Power Operation." Northrop Grumman, 13 April 2011.
Nanoscale
GaN nanotubes and are proposed for applications in nanoscale electronics, optoelectronics and biochemical-sensing applications.
Spintronics potential
When doped with a suitable transition metal such as manganese, GaN is a promising spintronics material (magnetic semiconductors).
Synthesis
Bulk substrates
GaN crystals can be grown from a molten Na/Ga melt held under 100 atmospheres of pressure of N2 at 750 °C. As Ga will not react with N2 below 1000 °C, the powder must be made from something more reactive, usually in one of the following ways:
Jian-Jang Huang, Hao-Chung Kuo, Shyh-Chiang Shen (2025). 9780857099303, Woodhead. ISBN 9780857099303
Metal-organic vapour phase epitaxy
Blue, white and ultraviolet LEDs are grown on industrial scale by metalorganic vapour-phase epitaxy (MOVPE). The precursors are ammonia with either trimethylgallium or triethylgallium, the carrier gas being nitrogen or hydrogen. Growth temperature ranges between . Introduction of trimethylaluminium and/or trimethylindium is necessary for growing quantum wells and other kinds of .
Molecular beam epitaxy
Commercially, GaN crystals can be grown using molecular beam epitaxy or MBE. MBE growth of GaN can be divided into two catagories, including ammonia-MBE (NH3-MBE) and plasma assisted MBE (PA-MBE). In NH3-MBE, NH3 is used as the nitrogen source, while a nitrogen RF plasma is used in PA-MBE. This process can be further modified to reduce dislocation densities. First, an ion beam is applied to the growth surface in order to create nanoscale roughness. Then, the surface is polished. This process takes place in a vacuum. Polishing methods typically employ a liquid electrolyte and UV irradiation to enable mechanical removal of a thin oxide layer from the wafer. More recent methods have been developed that utilize solid-state polymer electrolytes that are solvent-free and require no radiation before polishing.
Safety
GaN dust is an irritant to skin, eyes and lungs. The environment, health and safety aspects of gallium nitride sources (such as trimethylgallium and ammonia) and industrial hygiene monitoring studies of MOVPE sources have been reported in a 2004 review.
See also
External links
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