The power efficiency, size, weight, and low costs offered by GaN devices make them the most promising WBG material in use.
Due to high electron mobility, GaN sustains high voltages with current flowing faster than Si.
GaN-on-Si technology can integrate with other Si-based devices, opening the door to compact and high power density designs in power semiconductor devices.
GaN devices are regularly used in some converters and drive applications
Wide-bandgap (WBG) devices are increasingly used in 600 V range applications, as they offer superior performance in terms of losses, operating temperatures, and frequency. WBG technology is often found in devices based on silicon carbide (SiC) and gallium nitride (GaN). The last few years have seen tremendous advancements resulting in improved GaN technology—especially in GaN on silicon-based devices. GaN devices are also being used in 200-600V range converters or drive applications, 5G circuits, electric vehicles, etc. In this article, we will explore the recent advancements made to improve GaN technology.
Wide-Bandgap Semiconductor Devices
WBG devices offer superior material properties that allow operation under high temperature, high voltage, high current, and high switching speed. The performance of WBG devices is much better than conventional semiconductors, making them widely used in consumer electronics, renewable energy converter systems, electric vehicle chargers, power supplies, and telecommunication systems. There are numerous materials offering WBG properties, however, the power efficiency, size, weight, and low costs offered by SiC and GaN devices make them the most promising WBG materials in use.
While the semiconductor industry completely revolved around Si and Si compounds in the last decade, GaN-based devices offer better performance and cost benefits.
GaN Technology Improvements
The semiconductor compound GaN has tremendous potential compared to silicon and its compounds. Because of this, GaN technology is taking over the position of Si in the semiconductor industry. Below is a table comparing the material properties of GaN and SiC devices.
Material property values of SiC and GaN devices
The table above gives some material property values of SiC and GaN devices. At a material level, properties such as bandgap and the breakdown field strength of SiC and GaN are comparable, but with a vast contrast in the electron mobility value.
Due to high electron mobility, GaN sustains high voltages with current flowing faster than Si. The energy loss associated with GaN is significantly less. It is possible to design packages with more GaN in a given area. This helps in the downsizing of the chips, with impressive energy efficiency compared to Si counterparts. GaN technology aligns itself fairly well with Moore’s law.
The shift to GaN devices can save energy up to 15-20%. Apart from energy efficiency, GaN devices also possess excellent temperature withstanding capabilities. This thermal property is beneficial, as it gives more freedom in design, production, and applications.
Given these advantages, GaN devices are being commercialized for various industrial, automotive, aerospace, and military applications. The semiconductor industry is diverting some of its research and development to circuit topologies, system architectures, and packaging solutions based on GaN technology. Let’s look at one such advancement of GaN technology, GaN-on-Silicon, in the upcoming section.
Conventionally, GaN transistors are fabricated by epitaxially growing GaN layers on a bulk substrate. The quality of homoepitaxial growth of GaN layers depends on the characteristics and preparation of the bulk substrate. The biggest limiting factor of GaN-on-GaN vertical transistors is the high fabrication cost of homoepitaxially grown GaN. The heteroepitaxial growth of GaN on other substrates such as SiC, sapphire, and Si are options that are available.
Once GaN layers were epitaxially grown on Si bulk substrate, it paved the way for GaN-on-Si technology. The advantages of Si substrate, such as high thermal conductivity, existing fabrication facility, availability of a large wafer diameter, monocrystalline bulk substrate, and low costs, helped establish mass commercialization of GaN power devices, especially GaN-on-Si devices. GaN-on-Si technology is compatible with the integration of other Si-based devices, opening the door to compact and high power density designs in power semiconductor devices.
The demand for high power density designs is high, and GaN technology is gaining momentum. GaN power devices, especially the ones with heteroepitaxial grown GaN layers, are considered next-generation power semiconductor devices.
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