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The strength of wide bandgap materials for power electronics


By Ali Husain, Corporate Marketing & Strategy, ON Semiconductor P


ower electronic devices are vital to the operation of nearly every device that uses electricity, yet they are an underappreciated


segment of the semiconductor space. Generally, they are found in power


converter circuits that convert AC from the grid to DC voltage or between DC voltages, or run electric motors (DC to AC conversion), and more. Teir continuing improvement has increased the efficiency of every electronic device, and they are today considered crucial to enabling energy savings and carbon- reducing technologies such as LED lighting, solar power generation and electric vehicles.


Suitable materials Regularly found in power electronics today are semiconductor materials made from the so-called wide- bandgap (WBG) materials, Silicon Carbide (SiC) and Gallium Nitride (GaN). They gained their name due to their electron energy bandgap being wider than silicon’s, which lends them very beneficial characteristics such as lower electrical resistance and higher-frequency switching than the current power-workhorse IGBTs and MOSFETs.


Although oſten grouped together, in


reality SiC and GaN have important differences, with separate “sweet spots” where each material is most suitable. Wafer sizes are the first big difference:


SiC ingots are grown from a single- crystal seed wafer by chemical vapour deposition (CVD) or physical vapour transport (PVT). Both methods require high temperature and are slow compared to creating silicon ingots. SiC wafers also require slicing the ingot into disks. Since this is a very hard material and difficult to cut, even with a diamond saw, it proves challenging. Tere are several methods for ingot separation, but they can introduce defects into the single crystal. In contrast, GaN substrates are not cut


from ingots, but are grown by CVD on top of silicon wafers, itself a challenge since there’s a lattice mismatch between the two materials. Tere are methods to engineer this strain, but there is a risk of defects that affect reliability. Because GaN sits on top of the silicon, GaN power devices are considered “lateral”, i.e. their source and drain are on the same side of the wafer, in contrast to silicon and SiC power switches, where the main current path is vertical, through the chip.


Different strenghts SiC and GaN also have different optimal operating voltage levels. GaN devices,


rated for a breakdown voltage of about 100V will find uses in mid-voltage power conversion from 48V down, with applications in cloud computing and telecom infrastructure. Additionally, power supplies and wall-warts will contain 650V GaN power switches, the right voltage rating for AC-to-DC conversion with the wide input voltage range of 90-240VAC. Te high- frequency ability of GaN allows the passive components of the power supply to be significantly smaller, resulting in a much more compact solution overall. By contrast, SiC devices are designed


for 650V and above. At 1200V and higher SiC becomes the best solution for many applications, such as solar inverters, electric vehicle chargers and industrial AC to DC conversion. Another long-term application is the solid-state transformer, replacing the current copper and magnet transformers with semiconductors.


Power revolution The next revolution in power electronics is already upon us. The promising wide-bandgap materials silicon carbide and gallium nitride will help make the future of power electronics more efficient and more compact for a wide variety of applications.


IN THE NEXT ISSUE OF ELECTRONICS WORLD, THE COMBINED JULY-AUGUST EDITION Special reports include


Design with sensors • Embedded design • Power-saving techniques and systems • Displays • Enclosures • Connectors


There are also the usual regular columns, focusing on embedded design, converter interfaces and green and sustainable electronics, as well as a brand new section called Circuit Drill, which covers circuit analysis and troubleshooting at the workbench. Don’t miss out, subscribe now by contacting data@datateam.co.uk. More information and technical material are available on the Electronics World website at


www.electronicsworld.co.uk 04 June 2021 www.electronicsworld.co.uk


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