Fabrication of Pyramid Structure Substrate Utilized for Epitaxial Growth Free-Standing GaN

Abstract

Metal-organic chemical vapor deposition (MOCVD)-grown GaN on sapphire substrate was etched by hot phosphoric acids. Pyramid structures were obtained in the N-polar face of the MOCVD-GaN. Details of the formation process and morphology of the structures were discussed. The crystallographic plane index of the pyramid facet was calculated dependent on the symmetry of the wurtzite crystal structure and the tilt angle. The substrates with pyramid structures were utilized in subsequent hydride vapor phase epitaxy (HVPE) growth of GaN. Free-standing crystals were obtained, while HVPE-grown GaN achieved a certain thickness. Raman spectroscopy was employed to obtain the stress conditions of the HVPE-GaN without and with sapphire substrate. The mechanism of the self-separation process was discussed. This facile wet etching method may provide a simple way to acquire free-standing GaN by HVPE growth.

Centimeter-Transferable III-Nitride Membrane Enabled by Interfacial Adhesion Control for a Flexible Photosensitive Device

“…25 As the interaction between III-nitride and 2D insertion layer is pure vdW force, the spontaneous delamination always happens during the cooling since their thermal expansion coefficients are different, 26,27 and it accompanies with the ruining of the III-nitride membrane. 28,29 On the other hand, the pristine 2D insertion layer is absent of dangling bonds, it is difficult for the III-nitride nucleation and growth. The artificial generation of defects or impurity atom doping via pre-treatment of the 2D insertion layer is carried out to activate nucleation sites.…”

“…Zhou et al and Jia et al also demonstrated the separation of the III-nitride membrane from graphene-coated sapphire, and the metal-insulator-semiconductor junction and violet LED were fabricated. , However, there are two extreme conditions of III-nitride spontaneous delamination or separation failure according to the unsuited vdWE interfacial adhesion, making it challenging for further applications . As the interaction between III-nitride and 2D insertion layer is pure vdW force, the spontaneous delamination always happens during the cooling since their thermal expansion coefficients are different, , and it accompanies with the ruining of the III-nitride membrane. , On the other hand, the pristine 2D insertion layer is absent of dangling bonds, it is difficult for the III-nitride nucleation and growth. The artificial generation of defects or impurity atom doping via pre-treatment of the 2D insertion layer is carried out to activate nucleation sites. − However, it is recognized as a destructive way to simultaneously cause the C–C bond breakage and lattice structure missing.…”