Pyramidal shape four V-grooved silicon substrate for enhancing cubic phase gallium nitride growth

This is the authors' abstract. We don't add key points for this paper.

Strong spontaneous polarization and piezoelectric effects in hexagonal gallium nitride (h-GaN) seriously limit the efficiency of h-GaN-based devices. To overcome this issue, a pyramidal-shaped four V-grooved silicon (4PVG-Si) patterned substrate is introduced for transforming h-GaN into cubic GaN (c-GaN) at the nanoscale. The purpose of using 4PVG-Si instead of simple V-grooved Si (VG-Si) is to improve the crystal quality with the maximum cubic volume of GaN. The growth of c-GaN was verified by high-resolution x-ray diffraction and cathodoluminescence, whereas high-resolution transmission electron microscopy (HRTEM) was further used to analyze the excessive and smooth c-GaN growth. The HRTEM images revealed that optimizing the growth of an aluminum nitride layer with 10–15 nm thicknesses promotes the maximum c-GaN volume. However, exceeding this thickness tended to the reduction in c-GaN volume, resulting in the development of big voids with abnormal tip-shaped growth. In the presence of big voids and abnormal tip-shaped growth, the hexagonal growth closed very late, and the cubic volume of c-GaN is reduced. To further promote the cubic phase of GaN, the growth conditions of GaN were also optimized. Our results proved that the design of 4PVG-Si and optimized growth conditions promote the maximum cubic volume of GaN.