Enhanced interfacial stability of GaN on SiC through contact orientation and layer tilting

Abstract

Gallium nitride (GaN) is typically grown on silicon carbide (SiC) or silicon (Si) substrates to form GaN-on-SiC or GaN-on-Si heterostructures; however, these systems often face fabrication challenges and significant lattice mismatch. Therefore, a comprehensive investigation of the GaN/SiC interface is essential for improving the structural stability and performance of GaN-on-SiC substrates. In this work, density functional theory calculations employing the plane-wave projector-augmented wave method and the generalized gradient approximation exchange-correlation functional, as implemented in Vienna Ab initio Simulation Package, were used to systematically investigate the interfacial structural stability of GaN-on-4H-SiC. Due to the complex stacking sequences of both GaN and 4H-SiC, atomic-scale compatibility plays a critical role in determining the interface stability. Our results show that GaN interfaced with the C-face of 4H-SiC exhibits lower total free energy and a reduced imaginary phonon fraction, indicating higher structural stability compared to the Si-face. Furthermore, tilting the GaN layer enhances dynamic stability, with 5° and 9° tilts reducing the imaginary component of the phonon spectrum by approximately 7.5%. These theoretical findings align well with recent experimental observations and provide valuable insights for interfacial engineering in high-performance GaN-on-SiC electronic devices.