Formation Mechanism of Self-Formed Triangular Pyramidal Patterns on Sapphire Substrate

Abstract

The current work reports the formation of a triangular pyramidal pattern on c-plane sapphire substrate by the sulfuric acid wet-etching process. The corner-up Al2(SO4)3 wet-etching reaction product formed on the sapphire substrate served as a natural mask to create the triangular pyramidal pattern. The nucleation plane of the corner-up Al2(SO4)3 was identified to be the (006) plane by SEM observation and XRD measurement. Energy-dispersive X-ray spectroscopy analysis shows the corner-up Al2(SO4)3 contains 0.78 at. % Zn. XRD diffraction analysis shows that the interplanar distance of the (006) plane of the Al2(SO4)3 reaction product increases by 1.18%. The increase in the interplanar distance of the (006) plane of the corner-up Al2(SO4)3 is caused by Zn substitution in Al2(SO4)3. Zn substitution in Al2(SO4)3 enhances the crystallographic matching between the c-plane surface and the (006) plane of Al2(SO4)3. Consequently, the probability of the formation of the corner-up Al2(SO4)3 reaction products increases with predissolving Zn in sulfuric acid etching solution. Both sapphire substrates with triangular and rectangular pyramidal patterns were fabricated as GaN LEDs. The output power of the GaN LEDs with triangular pyramidal pattern is higher than that of the GaN LEDs with the rectangular pyramidal pattern by 17.3%. We conclude that the higher output power of the GaN LEDs with the triangular pyramidal pattern is attributed to the higher light extraction efficiency, which corresponds to the larger divergence angle of the radiation pattern of the GaN LEDs with triangular pyramidal pattern.

Continuous Making, Stretch Breaking, and Exciton Dynamics of a Red-Emissive Organic Submicrometer-Sized Triangular Pyramid

“…On the other hand, the building up of tetrahedron structure can be rationalized by the layer-by-layer stacking of the triangular plates (Figure 4F). 57 However, the formation of planar triangular plates requires a geometrical orientation of 120°. In product molecule, amine and carbonyl group share a desired angle of 120°(Inset, Figure 4G).…”

Dislocation Etching Morphology on the A Plane of Sapphire Crystal

“…[ 1,2 ] However, crystal defects such as dislocation and stacking fault easily formed during sapphire crystal preparation, and these defects will severely limit the application of sapphire. Therefore, the characterization of crystal defects becomes particularly important, [ 3 ] which leads to the renaissance of chemical wet etching method.…”