Robust Heteroepitaxial Growth of GaN Formulated on Porous TiN Buffer Layers

Abstract

Gallium nitride (GaN) heteroepitaxial growth is widely studied as a semiconductor material due to its various benefits. Especially, development of a buffer layer between GaN and the substrate verifies to be an effective strategy to reduce high threading dislocation density. However, the buffer layer often impedes strong adhesion between the epilayer and foreign substrate because thermally induced residual stress often causes delamination of the epilayer during fabrication. Here, we developed a robust GaN heteroepitaxy employing a porous buffer layer formulated by hydride vapor phase epitaxy. A sufficiently low but completely coated thin Ti layer was deposited on the sapphire substrate, which led to a rough and porous TiN layer after nitridation. This porous structure enables the penetration of the GaN source into the porous structure, allowing GaN epitaxy initiation throughout the TiN layer. As a result, GaN crystal growth can fill the porous area during the GaN heteroepitaxy. Integrated visualization demonstrated that the voids were successfully removed by GaN infiltration, enabling the heteroepitaxial structure to show little deformation, confirmed by multiple indentations. Last, the void-free GaN heteroepitaxy with the porous TiN buffer layer displayed robust adhesion after delamination tests.