Page 30 - PEN eBook May 2022

Semiconductors AUTOMOTIVE

VERTICAL DEVICES UNDER RESEARCH

Imec will focus on improving the performance of the existing platform and perform further reliability
tests. The company currently offers a 200-V and 650-V platform for prototyping, soon to be followed

by 100 V. For GaN ICs with integrated components, a 1,200-V high-power platform may not yield
significant improvements. The higher the voltage, the slower the components become. Therefore, it
may not be necessary to integrate the driver on-chip; simulations will confirm this.

Imec is also looking into alternatives for discrete 1,200-V devices, enabling GaN technology for the
highest-voltage power applications, such as electric cars. Transistors with a lateral topology are
the dominant GaN device architecture today. These devices have their three terminals (source,
gate, and drain) at the surface in the same plane, so the electrical field is lateral, spanning the GaN
buffer layers and partly the back end (metallization, oxide). In a vertical device, the source and gate

are at the surface, while the drain is at the bottom of the epi stack. The electrical field in that case
flows through the whole stack. It is the source-drain separation that determines the breakdown
voltage of the device, and a larger separation safeguards the channel from breakdown. However,
larger distances between a laterally placed source and drain result in larger devices. Because the
chips for 1,200-V devices would become too large, lateral architectures are usually advised up Driving Advanced
to 650 V maximum. For a vertical device, on the contrary, going to higher voltages boils down to
creating a thicker epi stack because source and drain are located on different ends of the stack. Performance: Solutions

The chip’s surface area doesn’t increase.
for Electric Vehicles

By Dinesh Ramanathan, co-CEO of NexGen Power Systems

The idea of the electric vehicle is not new to today’s consumers. EVs have existed in a variety of
forms for almost two centuries. In the past few decades, however, as technology has advanced and
companies such as Tesla have found success — and as we grapple with the effects of climate change,

air pollution, and an ever-decreasing supply of fossil fuels — more consumers are considering EVs
than ever before.
For More Information

The growing popularity of EVs isn’t due solely to consumer demand. Governments around the world
have increasingly issued regulations and mandates, such as the Paris Agreement, to reduce carbon
▶ Imec demonstrates successful monolithic integration of Schottky diodes and
emissions in an effort to curb global warming.
depletion-mode HEMTs with 200 V GaN-IC

By the end of 2020, one study estimated that there were 10 million electric cars in operation
▶ Contact form to request paper presented at the IEDM 2021 conference across the globe. In fact, electric-car registrations increased by 41% that year, even though

worldwide, car sales overall dropped by 16% due to the Covid-19 pandemic. The same study found
▶ 200mm GaN-on-silicon technology and GaN power devices that approximately 3 million electric cars were sold globally in 2020 and that Europe overtook China
as the world’s largest EV market for the first time.

52 MAY 2022 | www.powerelectronicsnews.com MAY 2022 | www.powerelectronicsnews.com 53