Effect of nitridation temperature on formation and properties of GaN nanowall networks on sapphire (0 0 0 1) grown by laser MBE

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Solid-state materials for advanced technology, 2018-05, Vol.231, p.105-114
• Main Authors: Ramesh, Ch, Tyagi, Prashant, Yadav, B.S., Ojha, S., Maurya, K.K., Senthil Kumar, M., Kushvaha, S.S.
• Format: Article
• Language: English
• Subjects: Compressive properties; Crystal structure; Crystallinity; Emission analysis; Epitaxial growth; Field emission microscopy; Field emission scanning electron microscopy; Gallium nitrides; GaN nanowalls; High resolution X-ray diffraction; High temperature; Laser beams; Laser molecular beam epitaxy; Molecular beam epitaxy; Optoelectronics; Photoluminescence; Photoluminescence spectroscopy; Quantum size effect; Raman spectroscopy; Sapphire; Sapphire nitridation; Scanning electron microscopy; Size effects; Spectroscopic analysis; Spectrum analysis; Substrates; Tensile stress; X-ray diffraction
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2018.10.009

[Display omitted] •Growth of Heteroepitaxial GaN nanowalls is achieved using laser MBE at 700 °C.•GaN nanowalls network (NWN) are vertically well aligned with wall width of 8–20 nm.•Low X-ray rocking curve full width at half maximum along GaN(0 0 0 2) planes.•Nature of stress present in GaN is influenced by sapphire nitridation temperature.•A 94 meV enhancement of optical bandgap is obtained by PL for the GaN NWN. Vertical aligned GaN nanowall networks (NWN) have been grown on sapphire (0 0 0 1) substrates using laser assisted molecular beam epitaxy (LMBE) by tuning the sapphire pre-nitridation temperature (200–600 °C). Field emission scanning electron microscopy studies showed the formation of hexagonal shaped vertical GaN NWN with wall width of 8–20 nm on high temperature (600 °C) nitridated sapphire whereas flower shape granular GaN structure with grain size of 50–240 nm was obtained on low temperature (200 °C) nitridated sapphire. The crystalline properties of the GaN NWN have been studied using high resolution X-ray diffraction (HR-XRD). The results show that the full width at half maximum of the GaN(0 0 0 2) X-ray rocking curve has a relatively low value compared to previous reports of hetero-epitaxial grown GaN NWN on sapphire and other substrates. Raman spectroscopy measurements revealed the presence of compressive stress in film whereas tensile stress in GaN NWN structures which is also complimented by HR-XRD analysis. The room temperature photoluminescence spectroscopy measurement for NWN having tip width 8–20 nm showed a 94 meV blue-shift in near band edge emission, even though NWN experienced with tensile stress, which confirm the observation of quantum size effect. The hetero-epitaxial growth of porous GaN NWN with high crystalline quality holds promise for applications in field of nitride based sensors and the enhancement of light extraction efficiency in optoelectronics devices.