The CMOS fab-friendly and SEMI standard thickness 200 mm and 300 mm QST® (QROMIS Substrate Technology) substrates enable fabrication of commercial high-performance GaN devices with unmatched performance and application scale. This is achieved by utilizing a substrate core with the coefficient of thermal expansion (CTE) matched to GaN over a wide temperature range. Resulting fully integrated and low cost QST® substrates are breakage-free and enable a wide variety of power device architectures such as lateral, vertical, or integrated circuits with breakdown voltages ranging from 100 V to 2000 V. In addition, other GaN applications such as RF and microLED are realized on the same QST® manufacturing platform, enabling efficient manufacturing roadmap and profitable growth for the users. In this work, key advantages and manufacturing details of QST® substrate platform and GaN-on-QST® epitaxy will be discussed, as well as results from production of 200 mm QST®-based 650V E-mode GaN HEMT devices as the first commercially available device product. In addition, the QST®-based materials and device roadmap will also be presented.