What is gallium nitride (GaN)? – the next step in semiconductors

Gallium nitride (GaN) is a stable binary III/V wide-bandgap semiconductor material composed of gallium and nitrogen.

"Binary III/V" refers to a class of semiconductor materials that are composed of elements from groups III and V of the periodic table. The term "binary" indicates that these materials consist of two elements, one from group III and one from group V.

In the context of semiconductors, group III elements include aluminium (Al), gallium (Ga), and indium (In), while group V elements include nitrogen (N), phosphorus (P), arsenic (As), and antimony (Sb). When elements from these two groups combine, they form III-V semiconductors, known for their unique electronic and optical properties.

III-V semiconductors have several advantages over traditional silicon-based semiconductors, including higher electron mobility, direct bandgaps (which are efficient for light emission), and the ability to operate at higher frequencies and temperatures. These properties make III-V materials particularly valuable in specialised applications such as telecommunications, optoelectronics, and high-frequency electronics.

A "wide-bandgap" semiconductor refers to a material, like SiC or GaN, that has a larger energy gap between its valence band (where it is bound to an atom) and conduction band (where it can move freely and conduct electricity) compared to traditional semiconductors like silicon. The bandgap is a fundamental property of a semiconductor, determining its electrical and optical behaviour. In wide-bandgap materials, this energy gap is larger than that in traditional semiconductors. For example, silicon has a bandgap of about 1.1 electron volts (eV), while wide-bandgap materials like gallium nitride (GaN) have bandgaps around 3.4 eV.

Owing to the larger bandgap, semiconductors of this type can withstand far higher electric fields before breaking down. This property makes them ideal for high-power and high-voltage applications. Wide-bandgap materials can also operate at higher temperatures without losing their electronic properties, which is beneficial in environments with high thermal stress. Crucially, these materials are also able to switch on and off far faster than silicon, making them ideal for high-frequency applications such as radio frequency (RF) and microwave devices.

The origins of GaN

GaN has its origins all the way back in the early 20^th century, but significant progress in its development and application came later, driven by advancements in materials science and technology.

GaN as a material was first synthesised in the 1930s, however, the properties and potential of the material were not well understood at that time. The initial synthesis involved reacting gallium with ammonia at high temperatures.

GaN would have to wait until the 1960s before it gained any further attention or momentum, where, in the 1960s and 1970s, researchers began exploring its electronic and optical properties more systematically. The interest was spurred by the potential of GaN to emit blue and ultraviolet light, which was not possible with existing semiconductor materials like silicon and gallium arsenide.

The first successful creation of a GaN crystal was reported in 1971 by Maruska and Tietjen, who used a technique called chemical vapour deposition (CVD). This work was fundamental in demonstrating the feasibility of growing GaN crystals suitable for electronic applications.

Significant advancements in GaN technology occurred during the 1980s-1990s, particularly in Japan. Dr. Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura made groundbreaking contributions to GaN-based blue LEDs and laser diodes. Their work overcame significant challenges related to the material's crystal growth and doping, leading to the development of the first practical blue LEDs in the early 1990s.

The successful development of GaN LEDs had big impacts in the lighting and display industries, enabling the production of white LEDs and energy-efficient lighting. From here, GaN also found applications in power electronics, RF and microwave devices, and optoelectronics due to its superior properties, such as high efficiency, high breakdown voltage, and thermal stability.

Today, gallium nitride continues to be a critical material in various cutting-edge technologies, driving advancements in energy efficiency, telecommunications, and beyond. This is where we land with GaN in the semiconductor industry.

The advantages of GaN

GaN has many advantages over competitor and conventional materials in use today. As previously mentioned, being a wide-bandgap material has many advantages, allowing it to sustain higher voltages and electric fields without breaking down, crucial for high-power applications. This wide bandgap also contributes to GaN's superior thermal conductivity, enabling devices to operate at higher temperatures and dissipate heat more effectively, making them suitable for demanding environments.

Another significant advantage of GaN is its high efficiency. GaN transistors typically exhibit lower on-resistance compared to silicon transistors, resulting in reduced power loss and improved efficiency in power conversion applications. Furthermore, GaN devices can switch on and off faster than their silicon counterparts, which minimises energy losses during switching, particularly in high-frequency applications.

GaN's high electron mobility is another critical feature, allowing for faster electronic switching. This is especially beneficial in high-speed and high-frequency applications such as RF amplifiers and microwave devices, where rapid switching speeds are essential. The high electron mobility also contributes to lower conduction losses, enhancing the overall performance of electronic devices.

The efficiency and thermal properties of GaN enable the production of smaller and lighter electronic components. This compactness facilitates the design of more integrated and scalable systems, which is particularly advantageous in consumer electronics and portable devices. Additionally, GaN devices are known for their robustness, capable of handling over-voltage and over-temperature conditions better than many other semiconductor materials, thus offering enhanced durability and reliability.

GaN's high efficiency leads to significant energy savings, making it an ideal choice for power electronics, including power converters, inverters, and other energy management systems. The efficient heat dissipation of GaN devices also reduces the need for extensive cooling systems, which can lower costs and simplify designs.

GaN’s role in the semiconductor industry

GaN has been playing a significant and growing role in today’s semiconductor landscape due to its unique properties. High electron mobility, wide bandgap, and thermal stability make GaN suitable for a variety of high-performance and high-efficiency applications. Here’s a run down of some of the key areas where GaN is being most utilised:

Power electronics

GaN is current being widely deployed in power electronics, where its ability to handle high voltages and currents with lower losses makes it ideal for:

• Power supply units: GaN transistors are used in power adapters and chargers for consumer electronics, providing smaller, more efficient, and faster charging solutions.
• Power converters: In renewable energy systems, such a solar inverters and wind turbines, GaN helps to improve energy conversion efficiency.
• Electric vehicles: GaN components are used in EV powertrains, including onboard chargers and DC-DC converters, contributing to more efficient power management and longer driving ranges.

RF and microwave devices

GaN's high electron mobility and thermal conductivity make it suitable for high-frequency and high-power applications, including:

• 5G and telecommunications: GaN amplifiers are crucial in 5G base stations and other wireless communication systems, offering high efficiency and power density.
• Radar and satellite communications: GaN devices are used in radar systems, both military and civilian, and in satellite communications for their high output power and efficiency.

Optoelectronics

GaN is a key material in the optoelectronics field, particularly for devices that emit or detect light, such as:

• LEDs: GaN-based LEDs, particularly blue and ultraviolet LEDs, are used in displays, general lighting, and medical devices. GaN LEDs are also the basis for white LED lighting, which combines blue LEDs with phosphors.
• Laser diodes: GaN is used in laser diodes for applications in optical storage, such as Blu-ray discs, as well as in projectors and high-resolution printing.

Advanced computing & data centres

Data centres are ripe for GaN, efficiency in power conversion is increasingly valuable to this industry as it seeks to reduce energy consumption, improve thermal management, and reduce footprints within high-performance computing environments.

Consumer electronics

GaN is also seeing a high level of prevalence in consumer electronics, especially in the previously mentioned fast chargers for things like smartphones, laptops, and other portable devices. We are even seeing application of GaN in home appliances such as televisions, washing machines, and more.

Emerging applications

GaN's potential in emerging technologies such as quantum computing, solid-state lighting, and advanced sensors continues to be explored. As the technology matures and production costs decrease, the adoption of GaN in various sectors is expected to expand further.

Overall, GaN's role in the semiconductor industry is pivotal in driving innovations across a broad range of high-tech applications, offering enhanced performance and efficiency compared to traditional semiconductor materials like silicon. Alongside SiC, GaN is poised to become a massive part of the next generation of semiconductors.