Breakthrough result could pave way for GaN to enter into the SiC high voltage domain

Imec, the research and innovation hub, and AIXTRON, a provider of deposition equipment, have demonstrated epitaxial growth of gallium-nitride (GaN) buffer layers qualified for 1200V applications on 200mm QST substrates, with a hard breakdown exceeding 1800V.

The news that it is now possible to manufacture 1200V-qualified buffer layers opens doors to higher voltage GaN-based power applications such as electric cars, previously only feasible using silicon-carbide (SiC)-based technology. The result comes after the successful qualification of AIXTRON’s G5+ C fully automated metal-organic chemical vapor deposition (MOCVD) reactor at imec’s facility in Leuven, Belgium, for integrating the optimised material epi-stack.

Commenting Denis Marcon, Senior Business Development Manager at imec said, “GaN can now become the technology of choice for a whole range of operating voltages from 20V to 1200V. Being processable on larger wafers in high-throughput CMOS fabs, power technology based on GaN offers a significant cost advantage compared to the intrinsically expensive SiC-based technology.”

Over the years tremendous progress has been made with GaN-based technology, but achieving operating voltages higher than 650V has been difficult due to the difficulty of growing thick-enough GaN buffer layers on 200mm wafers. As a consequence, SiC has remained the Semiconductor of choice for 650-1200V applications – including for example electric cars and renewable energy.

Key to achieving the high breakdown voltage has been the careful engineering of the complex epitaxial material stack in combination with the use of 200mm QST substrates. The CMOS-fab friendly QST substrates from Qromis have a thermal expansion that closely matches the thermal expansion of the GaN/AlGaN epitaxial layers, that’s helped to pave the way for thicker buffer layers – and hence higher voltage operation.

Dr. Felix Grawert, CEO and President of AIXTRON said, “The successful development of imec’s 1200V GaN-on-QST epi-technology into AIXTRON’s MOCVD reactor is a next step in our collaboration with imec. Earlier, after having installed AIXTRON G5+C at imec’s facilities, imec’s proprietary 200mm GaN-on-Si materials technology was qualified on our G5+ C high-volume manufacturing platform, targeting for example high-voltage power switching and RF applications and enabling our customer to achieve a rapid production ramp-up by pre-validated available epi-recipes. With this new achievement, we will be able to jointly tap into new markets.”

Currently, lateral e-mode devices are being processed to prove device performance at 1200V, and efforts are ongoing to extend the technology towards even higher voltage applications.

Next to this, imec is also exploring 8-inch GaN-on-QST vertical GaN devices to further extend the voltage and current range of GaN-based technology.

Above: Vertical forward buffer leakage current measured on 1200V GaN-on-QST® at two different temperatures: (left) 25°C and (right) 150°C. Imec’s 1200V buffer shows vertical leakage current below 1µA/mm2 at 25°C and below 10µA/mm2 at 150°C up to 1200V with a breakdown in excess of 1800V both at 25°C and 150°C, which makes it suitable for the processing of 1200V devices.