The role of inversion domain boundaries in fabricating crack-free GaN films on sapphire substrates by hydride vapor phase epitaxy

• Atomistic simulations of inversion domain boundary (IDB) in GaN were performed.
• The existence of IDBs in GaN films leads to the reduction of the film stiffness.
• A sudden reduction of IDB density induces a strong tensile stress within the films.
• The density of IDB in GaN film can be controlled by adjusting GaCl/NH3 flow ratio.
• A microstructure of GaN buffer layer for minimization of stress was proposed.

Inversion domain boundaries (IDBs) are frequently found in GaN films grown on sapphire substrates. However, the lack of atomic-level understandings about the effects of the IDBs on the properties of GaN films has hindered to utilize the IDBs for the stress release that minimizes the crack-formation in GaN films. This study performed atomistic computational analyses to fundamentally understand the roles of the IDBs in the development of the stresses in the GaN films. A sudden reduction of the IDB density induces a strong intrinsic stress in the GaN films, possibly leading to the mud-cracking of the films. A gradual decrease in the IDB density was achieved by slowly reducing the GaCl flux during the growth process of GaN buffer layer on sapphire substrates, and allowed us to experimentally demonstrate the successful fabrication of 4-in. crack-free GaN films. This approach may contribute to the fabrication of larger crack-free GaN films.