High-mobility AlGaN/GaN heterostructures directly grown on diamond (111) substrates using a high-temperature physical-vapor-deposition AlN nucleation layer

The direct epitaxial growth of GaN on diamond substrates offers a fundamental solution for thermal management in high-power-density GaN electronic devices. However, the amorphous layer and the strong C-C bonds on the diamond (111) surface have persistently hindered high-quality III-nitride nucleation. In this work, we overcome this fundamental challenge through the development of high-temperature physical-vapor-deposited AlN (HT-PVD-AlN) nucleation technology. Our approach utilizes high temperatures to eliminate amorphous layers while employing high-energy plasma species to modify diamond surface bonds, resulting in an AlN nucleation layer with exceptional in-plane and out-of-plane crystallographic alignment. On top of this high-quality PVD-AlN nucleation layer, low-dislocation density GaN layers and high-mobility AlGaN/GaN heterostructures have been fabricated. The full width at half maximum values of the x-ray diffraction rocking curves for the GaN (0002) and (10 1¯ 2) planes are 651 and 788 arcsec, respectively. The AlGaN/GaN heterostructures grown on diamond substrates exhibit a record room-temperature electron mobility of 1640 cm2/(V s). This work demonstrates that GaN directly grown on diamond (111) by employing HT-PVD-AlN nucleation layer is promising for next-generation high-performance GaN electronic devices.