Growth Of Gallium Nitride Nanowires Research Articles

Controlled growth of gallium nitride nanowires on silicon and their utility in high performance Ultraviolet‑A photodetectors

Device fabrication using semiconductor nanostructures for detecting ultraviolet (UV) radiations, especially UV-A (320–400 nm) has received much attention both at laboratory level and in commercial endeavours. In this work, we have attempted catalytic growth of good quality gallium nitride nanowires (GaN NWs) for utilization in building high-responsive optoelectronic devices. In order to obtain good quality control in the growth of GaN NWs, single metal catalyst has been replaced with a binary catalytic alloy of gold-palladium (Au-Pd). Scanning electron microscopy (SEM) results revealed that the NWs grown are long, dense and uniformly thick in size. The hexagonal crystal structure of the grown NWs was confirmed using x-ray diffractometer (XRD) and transmission electron microscopy (TEM). Other characterization results like x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL) spectroscopy were helpful in determining the compositional and optical properties of the samples. The fabricated GaN NWs based UV-A photodetector showcased a fast rise time (τr) and fall time (τf) of around 22 and 29 ms, an ultrahigh responsivity (R) and sensitivity (S) of about of 11.87 × 107 A/W and 3.8 × 104%, an external quantum efficiency (EQE) of 9.45 × 109%, very high detectivity (D) of 3.83 × 1018 Jones and high wavelength selectivity in the UV-A regime.

Effects of experimental parameters on the growth of GaN nanowires on Ti-film/Si(1 0 0) and Ti-foil by molecular beam epitaxy

Gallium nitride (GaN) nanostructures are used in optoelectronic applications due to their unique optical and electronic properties. For some optoelectronic applications and potential photocatalytic systems, the growth of GaN nanowires on metallic substrates instead of expensive single crystalline semiconductors can be beneficial due to specific properties of metals. In this study, GaN nanowire systems were grown on 300 nm Ti-film/Si(100) and Ti-foil by plasma assisted molecular beam epitaxy (PA-MBE) and characterized in situ by Auger electron spectroscopy (AES) and ex situ by scanning electron microscopy (SEM). Effects of (i) the nature of substrate surface, (ii) Ga flux, and (iii) substrate temperature on the growth of GaN nanowires were investigated. Nearly vertical nanowires can be grown on Ti-films covered with amorphous TiOx or TiOxNy, which is formed during the nitridation process. To grow nearly vertical nanowires on Ti-foils, pre-nitridation of the substrate surface was found to be important. The orientation of GaN nanowires grown on nitridated Ti-foil is determined by the grain alignment of the original Ti-foil, however, GaN nanowires grown on nitridated Ti-foils are uniformly oriented to one direction within an individual grain, which is most likely due to the epitaxial relation between the nanowires and the underneath grains of the polycrystalline Ti-foils. Both the orientation and nanowire density vary on different grains.

Catalytic Growth of Gallium Nitride Nanowires on Wet Chemically Etched Substrates by Chemical Vapor Deposition.

Growth of gallium nitride nanowires on etched sapphire and GaN substrates using binary catalytic alloy were investigated by manipulating the growth time and precursor-to-substrate distance. The variations in behavior at different growth conditions were observed using X-ray diffractometer, Raman spectroscopy, X-ray photoelectron spectroscopy, cathodoluminescence spectroscopy, optical microscopy, atomic force microscopy, and scanning electron microscopy. It was noticed that, in respect of both the substrates, when growth time and/or precursor-to-substrate distance is increased, thickness of the nanowires around the etch pits remains unaltered, but there is variation in the density of nanowires. In addition, formation of gallium nitride microwires within the etch pits was also observed on etched sapphire substrates. Similarly, the thickness and density of the microwires were found to increase with increase in growth time and decrease with increase in precursor-to-substrate distance. The dimensionality scaling of gallium nitride was found to have a positive effect in improving the luminescence property and band gap of the grown nanowires. This method of nanowire growth can be helpful in increasing the probability of multiple reflections in the materials which makes them a suitable candidate for optoelectronic devices.

Selective area growth of GaN nanowires on Si(1 1 1) substrate with Ti masks by molecular beam epitaxy

We present results on the selective area growth (SAG) of Gallium Nitride (GaN) nanowires on Si substrate without any buffer layer by radio frequency plasma-assisted molecular beam epitaxy. Full selectivity was achieved with a thin Ti metal film used as a mask. The mask was fabricated with a lift-off method to avoid damage to the mask or Si substrate. The growth on the Ti film was totally suppressed at a low substrate temperature of 840 °C which is by far the lowest critical temperature for SAG. An InGaN thin layer was embedded in the GaN nanowires to realize a site controllable single photon source. Transmission electron microscopy (TEM) indicates single crystalline quality of defect-free GaN nanowires and the embedded InGaN quantum dot structure.

Growth of gallium nitride nanowires on sapphire and silicon by chemical vapor deposition for water splitting applications

Gallium nitride (GaN) nanowires (NWs) are one of the most promising candidates for photoelectrode materials due to their tunable band edge potentials and high stability in electrolytes. In this study, GaN NWs were grown on sapphire (Al2O3) (002) and silicon (Si) (111) substrate by chemical vapor deposition (CVD) method. High quality of GaN NWs on sapphire and silicon were confirmed by powder X-ray diffraction (XRD). Structural characterization of the synthesized NWs were performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The images revel the pristine and smooth surface of GaN NWs. Further, optical properties of GaN NWs were investigated at room temperature photoluminescence emission. The photocurrent density of GaN/Si NWs is found to be higher than that of GaN/Al2O3 NWs. The GaN/Si NWs having large surface area, are grown in a much simpler method. GaN/Si NWs are potential candidate for hydrogen energy generation, due to their enhanced water splitting efficiency by utilizing solar energy.

Growth of gold-palladium alloy catalyzed gallium nitride nanowires by chemical vapour deposition

The growth of gallium nitride nanowires on c-plane sapphire substrates using binary catalytic alloy was investigated by manipulating growth time and precursor-to-substrate distance. The variations in structural, optical and morphological behaviour of the samples at different growth conditions were observed using X-ray diffractometer, cathodoluminescence spectroscopy and scanning electron microscopy. It was noticed that, thickness of the nanowires decreased with increase in growth time and precursor-to-substrate distance. Simultaneously, length of the nanowires increased with growth time and varied with precursor-to-substrate distance. The reduction in nanowire thickness was found to have a positive effect in improving luminescence property and bandgap of the grown nanowires. The results indicate that this material system can be catered for optoelectronic device applications.

Growth behavior of GaN nanowires on c-plane sapphire substrate by applying various catalysts

Systematic reaction has been used to control the vapor–liquid–solid growth of gallium nitride nanowires (NWs) using different catalysts. GaN NWs were grown using Cu, Au, Pd/Au alloy catalysts on c-plane sapphire substrate. XRD and Raman analysis revealed the crystalline wurtzite phase of GaN synthesized at 900 °C. High density GaN NWs were studied using SEM and HRTEM. Elemental composition and impurities were analyzed by EDX. Diameter of individual NW, grown using Au catalyst is found to be ~50 nm. The diameter of NWs grown with the help of Cu catalyst was found to be ∼65 nm, whereas with Pd/Au catalyst, the diameter was about 100–200 nm. NBE emission observed from PL spectra for Cu catalyst (377 nm), Au catalyst (372 nm) as well as Pd/Au catalyst (385 nm) growth of GaN NWs respectively has been presented and discussed.

Fabrication Gallium Nitride (GaN) Nanowires by Thermal Chemical Vapor Deposition (TCVD) Technique

In this paper, low-dimensional gallium nitride (GaN) nanowires have been successfully grown on silicon substrate through thermal chemical vapor deposition (TCVD); no metal catalyst was used to assist growth of nanostructure. A high purity of gallium nitride powder was used as a starting material, evaporated at 1150 OC for 2 hour and then annealing at temperature 1000 OC under stable flow of ammonia (NH3) gas in horizontal quartz tube. The morphological investigation and crystalline and orientations growth of GaN nanostructure were carried out by employing scanning electron microscopy (SEM), high resolution X-ray diffractmeter (HRXRD). A room temperature micro-Raman spectrum were employed to study the optical properties and crystalline defects. XRD shows the diffraction peaks located at 2θ= 32.43, 34.57, 36.89, 48.05, 57.83, 63.62, 69.02, and 70.470 corresponding to the (100 ), (002), (101), (102), (110) , (103),(112 ) and (201) plane diffraction of GaN structure. These results revealed that the diffraction peaks can be attributed to hexagonal GaN phase with lattice constant of a = 3.190 A° and c = 5.1890 A°. Here we report on the growth of GaN nanowires on Si (111) substrate by CVD . This technique is much simpler and cheaper than such techniques as MBE, MOCVD and HVPE.

Using seed particle composition to control structural and optical properties of GaN nanowires

The morphology, structure, and optical properties of gallium nitride (GaN) nanowires grown using metal–organic chemical vapor deposition (MOCVD) on r-plane sapphire using gold and nickel seed particles were investigated. We found that different seed particles result in different growth rates and densities of structural defects in MOCVD-grown GaN nanowires. Ni-seeded GaN nanowires grow faster than Au-seeded ones, and they do not contain the basal plane stacking faults that are observed in Au-seeded GaN nanowires. We propose that stacking fault formation is related to the supersaturation and surface energies in different types of seed particles. Room temperature photoluminescence studies revealed a blue-shifted peak in Au-seeded GaN nanowires compared to the GaN near-bandgap emission. The blue-shifted peak evolves as a function of the growth time and originates from the nanowire base, likely due to strain and Al diffusion from the substrate. Our results demonstrate that seed particle composition has a direct impact on the growth, structure, and optical properties of GaN nanowires and reveal some general requirements for seed particle selection for the growth of compound semiconductor nanowires.

Suppressing the lateral growth of gallium nitride nanowires by introducing hydrogen plasma

In this study, we have found that the lateral homoepitaxial growth on GaN nanowires is suppressed by introducing hydrogen gas into the plasma-enhanced chemical vapor deposition (PECVD) apparatus for the growth of GaN nanowires. The formation of GaHx (x=2, 3) species due to the reaction between gallium atoms and hydrogen plasma is shown to decrease the amount of excess gallium atoms adsorbed on GaN nanowire surfaces, which results in the elimination of nucleation on the nanowire surface and thus improves the surface smoothness of the nanowire. The stacked-cone nanostructures appear under low hydrogen or hydrogen-less conditions, but completely disappear under high hydrogen conditions in the PECVD system. The mechanism of the elimination of lateral growth on the nanowire surface is further proposed.

Molecular beam epitaxial growth of gallium nitride nanowires on atomic layer deposited aluminum oxide

Semiconductor nanowires have received increasing focus from researchers due to their one dimensional characteristics, which offer new horizons for device designs. Nanowire growth has been shown to yield crystalline material on non-lattice matched substrates. Concerning gallium nitride nanowires, common growth substrates have been silicon (100) and (111) substrates. This manuscript discusses the successful molecular beam epitaxial growth of gallium nitride nanowires on amorphous aluminum oxide thin films, grown by atomic layer deposition. Results indicate that regardless of the amorphous nature of the oxide films, the gallium nitride nanowires grown are crystalline and free of defects even at the interface with the oxide. The results offer a method of realizing promising frontiers for device design in which a high quality crystalline material is desired on an amorphous substrate.

Growth and Characterization of High-Quality GaN Nanowires on PZnO and PGaN by Thermal Evaporation

In the current research, an easy and inexpensive method is used to synthesize highly crystalline gallium nitride (GaN) nanowires (NWs) on two different substrates [i.e., porous zinc oxide (PZnO) and porous gallium nitride (PGaN)] on Si (111) wafer by thermal evaporation without any catalyst. Microstructural studies by scanning electron microscopy and transmission electron microscope measurements reveal the role of the substrates in the nucleation and alignment of the GaN NWs. Further structural and optical characterizations were performed using high-resolution X-ray diffraction, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. Results indicate that the NWs have a single-crystal hexagonal GaN structure and growth direction in the (0001) plane. The quality and density of GaN NWs grown on different substrates are highly dependent on the lattice mismatch between the NWs and their substrates. Results indicate that NWs grown on PGaN have better quality and higher density compared to NWs on PZnO.

Influence of gas flow rates on the formation of III‐nitride nanowires

AbstractThis study achieved catalytic growth of gallium nitride nanowires (GaN‐NWs) and indium gallium nitride nanowires (InxGa1‐xN‐NWs) by the horizontal furnace chemical vapour deposition (HF‐CVD) method at the temperature of 900 °C and 550 °C, respectively. The morphologies and structures of III‐nitride nanowires depended on the gas flow rates were studied. Comparing the growth mechanisms of GaN‐NWs and InxGa1‐xN‐NWs, the vapour‐solid (VS) mechanism is dominant in GaN nanowires, except with a low ammonium flow rate, and the vapour‐liquid‐solid (VLS) mechanism is dominant in InxGa1‐xN nanowires. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Catalyst-Free GaN Nanowire Nucleation: Correlation of Temperature-Dependent Nanowire Orientation and Growth Matrix Changes

AbstractGrowth orientation and type of internal structures are both observed to change abruptly as a function of growth temperature in catalyst free growth of gallium nitride nanowires. In the present work, corresponding temperature-dependent changes in the growth matrix substrate that can affect the availability of nucleation sites and influence the reactivity of constituent adatom materials in catalyst-free nanowire growth are investigated. The influence of Ga vapor pressure and an abrupt change in the availability of single versus molecular adatom constituents is identified as a possible controlling parameter.

Selective growth of gallium nitride nanowires by femtosecond laser patterning

We report on gallium nitride (GaN) nanowires grown using pulsed laser ablation, adopting the vapor–liquid–solid (VLS) growth mechanism. The GaN nanowires are obtained based on the principle that a catalyst is required to initiate the nanowires growth. Locations of the GaN nanowires are patterned using femtosecond laser and focused ion beam. Scanning electron microscopy (SEM) is used to characterize the nanowires. This patterning of GaN nanowires will enable selective growth of nanowires and bottom-up assembly of integrated electronic and photonic devices.

Controlled Growth of Long GaN Nanowires from Catalyst Patterns Fabricated by “Dip-Pen” Nanolithographic Techniques

Long gallium nitride (GaN) nanowires were directly grown on SiO2 substrates from spatially defined locations using a chemical vapor deposition method. Locations of the GaN nanowires were well-controlled by using atomic force microscope (AFM)-based “dip-pen” nanolithography (DPN) and other patterning methods to precisely pattern catalyst islands on the substrate. Devices made of single GaN nanowires were fabricated and characterized. The convenient use of patterning techniques, especially the DPN technique, demonstrates a practical route to control the location of nanowires and for in situ fabrication of nanowire devices.