Controlling the morphology and optical properties of self-assembled InAsSb/InGaAs/InP nanostructures via Sb exposure (original) (raw)
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Journal of Applied Physics, 2013
A simple self-catalyzed and mask-free approach will be presented to grow GaN rods and nanorods based on the metal-organic vapor phase epitaxy technique. The growth parameter dependent adjustment of the morphology of the structures will be discussed. Rods and nanorods with diameters reaching from a few lm down to 100 nm, heights up to 48 lm, and densities up to 8Á10 7 cm -2 are all vertically aligned with respect to the sample surface and exhibiting a hexagonal shape with smooth sidewall facets. Optical properties of GaN nanorods were determined using cathodoluminescence. It will be shown that the optical properties can be improved just by reducing the Ga precursor flow. Furthermore, for regular hexagonal shaped rods and nanorods, whispering gallery modes with quality factors up to 500 were observed by cathodoluminescence pointing out high morphological quality of the structures. Structural investigations using transmission electron microscopy show that larger GaN nanorods (diameter > 500 nm) contain threading dislocations in the bottom part and vertical inversion domain boundaries, which separate a Ga-polar core from a N-polar shell. In contrast, small GaN nanorods ($200 nm) are largely free of such extended defects. Finally, evidence for a self-catalyzed, Ga-induced vapor-liquid-solid growth will be discussed. V C 2013 AIP Publishing LLC. [http://dx.
Self-assembled GaN nano-rods grown directly on (111) Si substrates: Dependence on growth conditions
Journal of Crystal Growth, 2005
We have investigated the growth condition, i.e. growth time and V/III ratio determining Ga-rich and N-rich conditions, influence on the formation of dislocation-free vertical GaN nano-rods grown on (1 1 1) Si substrate by molecular beam epitaxy. The hexagonal shape nano-rod with diameters ranging from o10 to 350 nm is fully relaxed from lattice strain, having a very good crystal quality characterized by dislocation-free lattice images observed by transmission electron microscopy (TEM) and extremely strong photoluminescence excitonic lines near 3.47 eV. The nano-rod starts to protrude after the formation of an approximately 0.4-mm thick columnar film base, and its density and physical dimension, i.e. diameter and height, are strongly dependent on V/III ratio and growth time. We have found that the hexagonal nano-rod can be formed on Si substrate, not only in N-rich condition but also even in a Garich condition, when it is formed without buffer layer at high growth temperatures.
Bulletin of Materials Science, 2010
Nanosized hexagonal InN flower-like structures were fabricated by droplet epitaxy on GaN/ Si(111) and GaN flower-like nanostructure fabricated directly on Si(111) substrate using radio frequency plasma-assisted molecular beam epitaxy. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the crystallinity and morphology of the nanostructures. Moreover, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) were used to investigate the chemical compositions and optical properties of nano-flowers, respectively. Activation energy of free exciton transitions in GaN nano-flowers was derived to be ~ 28⋅5 meV from the temperature dependent PL studies. The formation process of nanoflowers is investigated and a qualitative mechanism is proposed.
Self-assembled vertical GaN nanorods grown by molecular-beam epitaxy
Applied Physics Letters, 2003
Dislocation-free vertical GaN pillars in nanoscale were grown on Si ͑111͒ surface through self-assembly by molecular-beam epitaxy. No extra catalytic or nanostructural assistance has been employed. These nanorods have a lateral dimension from Շ10 nm to ϳ800 nm and a height of Շ50 nm to տ3 m protruding above the film, depending on the growth parameters. The top view of the nanorods has a hexagonal shape from scanning electron microscopy. Transmission electron microscopy shows that the nanorods are hexagonal, single crystal GaN along the c-axis. An extra peak at 363 nm originated from nanorods was observed in photoluminescence spectra at 66 K, which is ascribed to the surface states according to the results of surface passivation. Micro-Raman spectroscopy on a single nanorod reveals E 1 and E 2 modes at 559.0 and 567.4 cm Ϫ1 , respectively. Large strain was observed in both the transmission electron micrograph and the Raman shift. A possible growth mechanism is discussed.
Optical properties of self-assembled InGaN/GaN quantum dots
Materials Science and Engineering: B, 2001
Optical spectroscopy under varying temperature is used to investigate samples containing planes of self-assembled Ga 1 − x In x N quantum dots (0.15 Bx B 0.20), embedded in a GaN matrix. The samples have been grown by molecular beam epitaxy on sapphire substrates and the nano-islands have been obtained by the Stranski-Krastanov growth mode transition. Half-widths at half maximum as small as 0.05 eV are obtained for photoluminescence (PL) lines at T = 2 K. Increasing the growth time decreases the PL energy and drastically increases the PL decay time, as a result of the increasing of the average dot height. Time-resolved PL measurements with variable temperature allow us to observe the competitive influence of several mechanisms, namely the usual radiative and nonradiative recombination processes, plus the carrier feeding from random fluctuations, which plays a crucial role in the case of the larger dots. : S 0 9 2 1 -5 1 0 7 ( 0 0 ) 0 0 7 8 8 -1
Journal of Crystal Growth, 2003
We report on the growth and photoluminescence of InGaN/GaN multiple quantum wells (MQWs) grown on GaN nanocrystals embedded in amorphous SiN x ; grown on a p-type Si(1 0 0) substrate. p-Type Si(1 0 0) was thermally nitridated using NH 3 to form an amorphous SiN x layer in a metalorganic vapor phase epitaxy system. GaN nanocrystals were then grown on the SiN x layer, followed by the growth of InGaN/GaN MQWs on the GaN nanocrystals. These nanosize MQWs were capped with amorphous SiN x in a plasma enhanced chemical vapor deposition system. The findings show that nanosize InGaN/GaN MQWs can be embedded in amorphous SiN x grown on p-type Si(1 0 0) and that these self-assembled nanostructures may be used as new nanosize light-emitting sources as evidenced by photoluminescence from nanosize MQWs. r
Gallium Nitride Materials and Devices IX, 2014
We report on the properties and growth kinetics of defect-free, photoluminescence (PL) efficient mushroom-like nanowires (MNWs) in the form of ~30nm thick hexagonal-shaped InGaN-nanodisk on GaN nanowires, coexisting with the conventional rod-like InGaN-on-GaN nanowires (RNWs) on (111)-silicon-substrate. When characterized using confocal microscopy (CFM) with 458nm laser excitation, while measuring spontaneous-emission at fixed detection wavelengths, the spatial intensity map evolved from having uniform pixelated emission, to having only an emission ring, and then a round emission spot. This corresponds to the PL emission with increasing indium composition; starting from emission mainly from the RNW, and then the 540 nm emission from one MNWs ensemble, followed by the 590 nm emission from a different MNW ensemble, respectively. These hexagonal-shaped InGaN-nano-disks ensembles were obtained during molecular-beam-epitaxy (MBE) growth. On the other hand, the regular rod-like InGaN-on-GaN nanowires (RNWs) were emitting at a shorter peak wavelength of 490 nm. While the formation of InGaN rod-like nanowire is well-understood, the formation of the hexagonal-shaped InGaN-nanodisk-on-GaN-nanowire requires further investigation. It was postulated to arise from the highly sensitive growth kinetics during plasma-assisted MBE of InGaN at low temperature, i.e. when the substrate temperature was reduced from 800 o C (GaN growth) to <600 o C (InGaN growth), during which sparsely populated metal-droplet formation prevails and further accumulated more indium adatoms due to a higher cohesive bond between metallic molecules.
The Role of Si during the Growth of GaN Micro- and Nanorods
Crystal Growth & Design, 2014
The role of Si during the metal−organic vapor phase epitaxy of GaN rods is investigated. Already a small amount of Si strongly enhances the vertical growth of GaN. Reactive ion etching experiments show that the inner volume of the rod is much more strongly etched than the m-plane surface layer. Transmission electron microscopy and energy dispersive X-ray spectroscopy measurements reveal that Si is predominiantly incorporated in the surface layer of the m-plane sidewall facets of the rods. The formation of a SiN layer prevents growth on and etching of the m-planes and enhances the mobility of atoms promoting vertical growth. Annealing experiments demonstrate the extraordinary thermal resistivity in comparison to undoped GaN rod structures and GaN layers. The subsequent InGaN quantum well growth on the GaN rods reveals the antisurfactant effect of the SiN layer. A model based on the vapor−liquid−solid growth mode is proposed. The results help to understand the role of Si during growth of GaN rod structures to improve the performance of rod based light emitting and electronic devices.