GaN breakthrough at 1200V takes on SiC

April 29, 2021 // By Nick Flaherty
GaN breakthrough at 1200V takes on SiC
Imec and Aixtron have demonstrated 200 mm GaN epitaxy for 1200V applications for the first time with breakdown voltages over 1800V and have plans for vertical FETs

Research lab imec in Belgium has demonstrated a breakthrough gallium nitride (GaN) process on 200mm wafer that can take on silicon carbide (SiC) in high power 1200V designs for the first time.

Working with equipment from Aixtron, imec has demonstrated epitaxial growth of GaN buffer layers qualified for lateral transistors for 1200V applications on 200mm QST substrates, with a hard breakdown exceeding 1800V.

The result comes after the successful qualification of Aixtron’s G5+ C fully automated metal-organic chemical vapour deposition (MOCVD) reactor at imec for integrating the optimized material epi-stack. The lab as previously demonstated qualified enhancement mode high-electron-mobility transistors (HEMTs) and Schottky diode power devices have been demonstrated for 100V, 200V and 650V operating voltage ranges, paving the way for high-volume manufacturing applications.

However, achieving operating voltages higher than 650V has been challenged by the difficulty of growing thick-enough GaN buffer layers on 200mm wafers. Therefore, SiC has so far been the wideband semiconductor of choice for 650-1200V applications, in particular for inverters in electric cars and renewable energy.

“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,” said Denis Marcon, Senior Business Development Manager at imec.

The key to the high breakdown voltage is the careful engineering of the complex epitaxial material stack in combination with the use of 200mm QST substrates that were developed in the IIAP programme with Qromis. These wafers have a thermal expansion that closely matches the thermal expansion of the GaN/AlGaN epitaxial layers, paving the way for thicker buffer layers for the higher voltage operation.

“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,” said Dr. Felix Grawert, CEO and President of Aixtron. “Having installed the G5+C at imec’s facilities, imec’s proprietary 200mm GaN-on-Si materials technology was qualified on the 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.”

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 building vertical GaN devices on the 200mm GaN-on-QST wafers to further extend the voltage and current range of GaN-based technology.

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Picture: 
A 200mm QST GaN wafer

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