Low-stress MOCVD-grown 15 μm GaN layers on 200 mm engineered substrates with minimal wafer bow

Abstract

Gallium nitride is increasingly recognized as a leading material for power and radio frequency applications, due to its unique electronic properties. However, the phenomenon of wafer bow and warpage during GaN growth on heterogeneous substrates presents significant challenges for vertical-type GaN devices with increasing drift layer thickness (for high voltage applications, 1200 V and above) and substrate diameters scaling to 200 mm. In this study, we introduce a growth scheme in the metalorganic chemical vapor deposition of GaN on 200 mm “engineered” substrates from Qromis substrate technology, specifically to minimize the wafer bow for vertical GaN metal-oxide-semiconductor field-effect transistors featuring an 11.5 μm-thick drift layer, with an overall GaN stack of ∼15 μm. By systematically reducing the pressure during the growth of unintentionally doped GaN from 300 to 150 mbar on an Al0.3Ga0.7N buffer layer, the tensile stress induced during cooldown could be effectively compensated. This yields an overall low residual stress of the thick ∼15 μm epitaxially grown GaN layers on the engineered Qromis substrate technology® substrate.