Characterization of free‐standing GaN substrates prepared by self lift‐off

Abstract

Free-standing GaN layers were successfully prepared by self lift-off process. Single crystalline ZnO buffer layer and GaN layer were successively grown on sapphire substrate by plasma assisted molecular beam epitaxy. Thick GaN film was grown on this template substrate for the realization of stress-free freestanding substrate by hydride vapor phase epitaxy. The a-axis and c-axis lattice constants of free-standing GaN were 3.189Å and 5.185Å, respectively. Peak positions of photoluminescence spectrum were D 0 X of 3.4715 eV and FX A of 3.4791 eV. These results suggest that the stress-free GaN layers were successfully prepared by self lift-off process.

Fabrication of a freestanding GaN layer by direct growth on a ZnO template using hydride vapor phase epitaxy

“…Therefore, new approaches have recently been developed: self-separation of the evaporable buffer layer (EBL) [7] and chemical lift-off using a metal-nitride [8]. However, these methods are associated with several problems that arise from the narrow growth window of the amorphous (NH 4 Cl) layer and the different crystal structures of the metal-nitride template [7,8]. Therefore, it is important to develop simpler ways to grow and separate the GaN layer.…”

“…However, the laser lift-off technique often results in fracturing during laser irradiation [4], and the other approaches require complex processes such as deposition of mask materials and growth of a GaN template prior to growth of the thick GaN layer. Therefore, new approaches have recently been developed: self-separation of the evaporable buffer layer (EBL) [7] and chemical lift-off using a metal-nitride [8]. However, these methods are associated with several problems that arise from the narrow growth window of the amorphous (NH 4 Cl) layer and the different crystal structures of the metal-nitride template [7,8].…”