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<i>β</i> -Ga <sub/>2</sub> O <sub/>3</sub> thin film grown on sapphire substrate by plasma-assisted molecular beam epitaxy
摘要： Monoclinic gallium oxide (Ga2O3) has been grown on (0001) sapphire (Al2O3) substrate by plasma-assisted molecular beam epitaxy (PA-MBE). The epitaxial relationship has been confirmed to be [010](ˉ201)β-Ga2O3||[1ˉ100](0001)Al2O3 via in-situ reflection high energy electron diffraction (RHEED) monitoring and ex-situ X-ray diffraction (XRD) measurement. Crystalline quality is improved and surface becomes flatter with increasing growth temperature, with a best full width at half maximum (FWHM) of XRD ω-rocking curve of (ˉ201) plane and root mean square (RMS) roughness of 0.68° and 2.04 nm for the sample grown at 730 °C, respectively. Room temperature cathodoluminescence measurement shows an emission at ~417 nm, which is most likely originated from recombination of donor–acceptor pair (DAP).
关键词： CL measurement,β-Ga2O3,sapphire substrate,PA-MBE,crystalline quality
更新于2025-09-23 15:22:29
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An investigation of aluminum nitride thin films patterned by femtosecond laser
摘要： In this study, a femtosecond laser etching method is proposed to pattern an aluminum nitride (AlN) ?lm, grown by metal-organic chemical vapor deposition on sapphire. Via control of typical pulse energies, the designed pattern was precisely written in the AlN ?lm. The morphology of the patterned structures was characterized using a three-dimensional laser scanning confocal microscope and a scanning electron microscope; crystalline quality and ?lm strain were analyzed using a Raman spectrometer and a transmission electron microscope. The results indicate that consistent morphologies were achieved with only slight changes to the crystalline quality. The tensile stress of the AlN ?lm was released, and the ?lm surface was slightly compressed after laser patterning. Thus, femtosecond etching has the potential to be an in situ patterning method during ?lm growth.
关键词： film strain,patterning,crystalline quality,femtosecond laser,aluminum nitride,thin films
更新于2025-09-23 15:19:57
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Thermally annealed wafer-scale h-BN films grown on sapphire substrate by molecular beam epitaxy
摘要： The effect of high temperature annealing (HTA) on crystalline quality improvement of h-BN films grown on sapphire substrates has been investigated. It is found that BN grown using conventional molecular beam epitaxy is disordered due to the growth temperature below 1000 °C. By annealing at a temperature of 1700 °C, thermodynamically stable crystalline h-BN could be obtained at wafer scale, where diffusion of atoms in the as-grown BN film is enhanced and the structural defect density decreases. The crystalline h-BN has been confirmed by x-ray diffraction, Raman scattering, and atomic force microscopy measurements. This work demonstrates that HTA is a simple and effective way to achieve wafer-scale crystalline h-BN films, which have numerous potential applications in next-generation two-dimensional devices and flexible III-nitride optoelectronic devices.
关键词： crystalline quality,molecular beam epitaxy,sapphire substrate,h-BN films,high temperature annealing
更新于2025-09-19 17:13:59
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Growth of InGaN films on hardness-controlled bulk GaN substrates
摘要： We carried out an evaluation of the crystalline quality of bulk GaN substrates and the properties of InGaN ?lms grown on them. The Urbach energy estimated by photothermal de?ection spectroscopy and the tail states near the valence band maximum determined by hard x-ray photoemission spectroscopy were larger for hardness-controlled bulk GaN (hard GaN) than those for conventional bulk GaN (conventional GaN). However, InGaN on hard GaN grows in a step-?ow-like mode, while InGaN grown on conventional GaN exhibits spiral-like growth. The photoluminescence decay at room temperature for InGaN grown on the hard GaN was 470 ps, compared with 50 ps for that grown on the conventional GaN. This can be attributed to the suppression of spiral-like growth due to the resistance to deformation of the hard GaN. These results indicate that substrate hardness is one of the most important factors for III–V nitride growth on the bulk GaN substrate.
关键词： hard x-ray photoemission spectroscopy,photoluminescence,bulk GaN substrates,InGaN films,photothermal de?ection spectroscopy,crystalline quality
更新于2025-09-11 14:15:04
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Effects of 6H-SiC Substrate Polarity on the Morphology and Microstructure of AlN Films by HVPE with Varied V/III Ratio
摘要： AlN films grown by high temperature hydride vapor phase epitaxy (HVPE) on Si-face and C-face 6H-SiC substrates were investigated. The influences of the substrate polarity with varied V/III ratio on growth mode, structural characteristics and crystalline quality of hetero-epitaxial AlN films have been studied. With the increasing of V/III ratio, AlN grown on Si-face 6H-SiC substrates changed the growth mode from step-flow to 3D island growth, and correspondingly, its surface morphology got rougher. On the contrast, AlN on C-face substrates were consistently in 3D growth mode and maintained a relatively rough surface, with a high density of nanotubes generated, each of which consisting of hexagonal sides defined by {01 0} facets and locating at the bottom of a V-shaped pit on the surface. Based on XRD, Raman and TEM analyses, it was found that the best AlN layer quality was obtained on the Si-face 6H-SiC at V/III ratio of 10.
关键词： Crystalline quality,Morphology,Dislocations,Substrate polarity,Nanotubes,Growth mode
更新于2025-09-11 14:15:04
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Reduction in crystalline quality anisotropy for non-polar a-plane GaN directly grown on titanium patterned sapphire substrate
摘要： Nonpolar a-plane GaN films were directly grown on titanium patterned sapphire substrates (Ti-PSS) by metalorganic chemical vapor deposition (MOCVD). It is demonstrated that the GaN film grown on Ti-PSS has superior surface quality and less surface pits than that on flat sapphire substrate. More importantly, the anisotropic behavior of the X-ray rocking curve-full width at half maximum values for the on-axis reflections were significantly improved. It is found that, the increased mosaic block size along m-direction could be the main reason for the reduction in the crystalline quality anisotropy. This work provides a simple and effective method to improve the crystal quality of non-polar GaN films.
关键词： X-ray rocking curve,crystalline quality anisotropy,MOCVD,titanium patterned sapphire substrates,Nonpolar a-plane GaN
更新于2025-09-10 09:29:36