The QST substrate—a 300mm GaN growth platform developed by Shin-Etsu Chemical Co. Ltd—has been adopted for IMEC’s 300mm GaN power device development program, where sample evaluation is currently underway. In these evaluations, a 5 µm-thick HEMT device fabricated on a QST substrate achieved a record-setting breakdown voltage exceeding 650V for a 300mm wafer.

Shin-Etsu Chemical, licensed by QROMIS Inc., manufactures 150mm and 200mm QST substrates, as well as GaN-on-QST epitaxial wafers in multiple diameters. In September 2024, the company began providing 300mm QST samples through a joint initiative with QROMIS. Shin-Etsu Chemical and QROMIS have since strengthened their partnership to supply 300mm QST substrates to IMEC’s state-of-the-art 300mm CMOS fab in Leuven, Belgium.

IMEC officially launched its 300mm GaN power device development program in October 2025, announcing plans to develop GaN power devices on 300mm QST substrates. The institute has already developed a 650 V-rated device and is progressing toward a 1,200 V-class model targeting AI data centers, industrial systems, and automotive applications.

Initial evaluation results show that IMEC successfully fabricated a 5 µm-thick high-voltage GaN HEMT structure on Shin-Etsu Chemical’s 300mm QST substrate—fully compliant with SEMI standards—using Aixtron’s Hyperion MOCVD system. The device achieved a world-record breakdown voltage above 800V, far surpassing the 650V benchmark for SEMI-standard substrates, while maintaining excellent in-plane uniformity. These results confirm that QST substrates, engineered with a thermal expansion coefficient matched to GaN, enable stable, high-quality GaN crystal growth even at large wafer diameters.

Although existing silicon wafer lines can be used for GaN processing, yield degradation at larger diameters—caused by issues such as wafer warpage—has limited the feasibility of mass production on silicon. The 300mm QST substrate overcomes these limitations by enabling thick-film GaN epitaxy for high-voltage applications without warping or cracking—capabilities unattainable with silicon substrates—thereby significantly reducing device cost. Shin-Etsu Chemical continues to expand its 150mm and 200mm QST production capacity and is progressing toward mass production of 300mm QST substrates.

QST substrates are now being evaluated by numerous domestic and international customers for use in power, high-frequency, and LED devices, with growing interest driven by the rising demand for AI data-center power solutions.

With a lineup spanning 150mm to 300mm, QST substrates are poised to accelerate the adoption of next-generation GaN devices. Shin-Etsu Chemical remains committed to advancing the deployment of GaN technologies—essential to the sustainable, energy-efficient society of the future.