Gallium nitride (GaN) is a compound semiconductor consisting of gallium, nitrogen and arsenic. It is a wide bandgap semiconductor with a bandgap of 3.4 eV, higher than silicon (1.1 eV) and gallium arsenide (1.4 eV). This wide bandgap gives GaN power benefits such as higher breakdown voltage, higher electron mobility, and higher operating temperature.
Physical and Structural Properties
GaN crystallizes in the wurtzite crystal structure. Gallium and nitrogen atoms are covalently bonded together in a hexagonal crystal lattice. The crystal planes of GaN are nonpolar, meaning there is no intrinsic electric field in the material that would limit performance. GaN has a melting point of over 2500°C and is a very hard material, rated 9 on the Mohs hardness scale.
These physical properties make GaN Semiconductor very robust and durable. It can continuously operate at much higher temperatures than silicon. Furthermore, the crystal structure allows efficient electron transport, enabling fast switching. Overall, the material properties give GaN significant power semiconductor advantages over existing silicon and gallium arsenide technologies.
GaN in Power Electronics
GaN is well-suited for power electronic applications in areas such as power supplies, renewable energy conversion, electric vehicles, and transportation systems. With a bandgap almost three times larger than silicon, GaN transistors can switch on and off much faster while supporting operation at higher voltages.
Some examples where gallium nitride is making an impact include computer power supplies, LED lighting, photovoltaic solar inverters, and electric vehicle chargers. By reducing losses and size, GaN implementations are delivering power systems that are more efficient, compact, and affordable. GaN is projected to eventually replace silicon in many power conversion applications up to 1200V.
GaN Transistors - HEMTs and MISHEMTs
The most common GaN-based transistors are high electron mobility transistors (HEMTs). These utilize the spontaneous and piezoelectric polarization effects at the AlGaN/GaN interface to create a two-dimensional electron gas with high carrier density and mobility. This enables HEMTs to achieve very low on-resistances.
Another emerging transistor structure is the metal-insulator-semiconductor HEMT (MISHEMT). An insulating oxide layer is incorporated at the gate to reduce the effects of current collapse plaguing regular HEMTs. The oxide provides a better interface for the gate contact, improving manufacturing reliability.
MISHEMTs offer lower gate leakage, fewer current collapse issues, and simpler driving requirements. They can operate at higher temperatures with even lower losses. Advanced MISHEMT designs will help accelerate the adoption of gallium nitride in high-voltage power conversion applications up to the 1200V range.
GaN Manufacturing and Cost Trends
While GaN manufacturing is still maturing compared to silicon, significant progress has been made in lowering costs and enhancing yields. Epitaxial wafer size has increased to 150mm and 200mm diameters for larger economies of scale. New deposition technologies like MOCVD allow for more uniform thin films with fewer defects.
Wafer fabs are able to produce over 10,000 GaN HEMT wafers per month cumulatively. GaN-on-Silicon is becoming the preferred substrate approach due to lower cost compared to native gallium nitride growth on sapphire or silicon carbide. Packaging is evolving as well, with new techniques to optimize thermal conductivity.
Industry analysts project GaN semiconductor costs could reach parity with silicon within 5 years as production volume climbs exponentially. Wide bandgap technologies traditionally follow a steep experience curve, so initial high costs fall rapidly. As more applications adopt GaN, its utilization rate will rise, benefiting both manufacturers and consumers through lower prices.
The growth opportunities for gallium nitride semiconductors are immense across several multi-billion dollar markets including power supplies, renewable energy, electric vehicles, rail traction, and others. Independent forecasts estimate the total GaN power device market size may surpass $1 billion by 2025.
GaN’s superior material properties allow for more efficient, higher density power conversion while enabling entirely new system capabilities. Transitioning from silicon and other traditional semiconductor technologies may take time, but innovators developing next-generation electric power systems now have a game changing material to work with. Ultimately, GaN promises to accelerate global progress toward sustainable energy and transportation infrastructures.
As manufacturers continually optimize cost and yield, and more innovative products emerge, gallium nitride semiconductors will become even more prevalent. Within this decade, GaN is positioned to transform mainstream power electronics applications. The future of high-efficiency power systems will be built upon this wide bandgap semiconductor technology.
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