Growth Of InN Research Articles

MBE Growth and Optical Properties of GaN, InN, and A3 B5 Nanowires on SiC/Si(111) Hybrid Substrate

The possibility of GaN, InN, and A3B5 nanowires MBE growth on a silicon substrate with a nanoscale SiC buffer layer has been demonstrated. Optical studies indicated a higher structural quality GaN NWs compared with the best structures of GaN NWs without silicon carbide buffer layer. The diameter of A3B5 NWs is smaller than diameter of similar NWs which were grown on a silicon substrate, because of higher lattice mismatch. In particular, InAs NWs diameter was evaluated as little as 10 nm, one of the smallest ever demonstrated for this NWs system.

Epitaxial growth of semipolar InN() on LaAlO3 substrate: Epitaxial relationship analysis

Epitaxial semipolar InN() crystals were grown on a LaAlO3(112) substrate using radio frequency plasma-assisted molecular beam epitaxy without any interlayer. The lattice mismatch between InN and LaAlO3 was estimated to be −7.75% along the []InN direction and 0.2% along the []InN direction. The InN film is epitaxic with the LaAlO3 substrate, with orientation relationships between InN() ∥ LaAlO3(112) and []InN ∥ []LAO. InN grown on LaAlO3(112) appears () plane orientated, with two types of domains. Semipolar InN() layers can be grown at 510 °C and show X-ray rocking curve FWHMs of 1830 and 1408 arcsec for InN(0002) and InN(), respectively. However, InN grown at 510 °C has the highest peak intensity and the narrowest FWHM of the prepared samples, indicating high-quality crystal growth.

Low-temperature (≤600 °C) growth of high-quality InxGa1−xN (x ∼ 0.3) by metalorganic vapor phase epitaxy using NH3 decomposition catalyst

InxGa1−xN (x ∼ 0.3) films on GaN/sapphire templates were grown by NH3 decomposition catalyst-assisted metalorganic vapor phase epitaxy (CA-MOVPE). NiO-based pellets were used as a catalyst. Even at a temperature lower than 500 °C, single-crystal In0.3Ga0.7N films were grown without the incorporation of metallic components (In, Ga) or the cubic phase. In contrast with the case of InN growth using the same catalyst [A. Yamamoto et al., Jpn. J. Appl. Phys. 55, 05FD04 (2016)], no marked grain growth or hydrogen etching was observed in In0.3Ga0.7N. Samples grown at a temperature ≤500 °C showed a full-width at half-maximum of the (0002) X-ray rocking curve as small as 10 arcmin or smaller. The carrier concentration in nominally undoped In0.3Ga0.7N grown using the catalyst was higher by about 4 orders of magnitude than that in conventional MOVPE samples. Secondary ion mass spectroscopy analysis revealed that such a higher carrier concentration was due to the marked reduction in carbon contamination level in the films.

Site-controlled crystalline InN growth from the V-pits of a GaN substrate

A site-controlled crystalline InN growth from the V-pits of a GaN substrate was investigated. The V- pits were fabricated by epitaxial lateral growth of GaN over SiO2 disks patterned on a sapphire substrate. InN crystals were found to preferably grow on the inclined {10–11} crystal planes of the V-pits. A V-pit size of 1μm or less can provide precise site-controlled InN nucleation at the V-pit bottom, while no InN was grown on the rest of the exposed GaN surfaces. The site-controlled nucleation is attributed to the low surface energy point created by the converging six {10–11} crystal facets at the V-pit bottom. When In source supply is below a certain value, this V-pit bottom is the only location able to aggregate enough active sources to start nucleation, thereby providing site-controlled crystal growth.

Morphology Controlled Fabrication of InN Nanowires on Brass Substrates.

Growth of semiconductor nanowires on cheap metal substrates could pave the way to the large-scale manufacture of low-cost nanowire-based devices. In this work, we demonstrated that high density InN nanowires can be directly grown on brass substrates by metal-organic chemical vapor deposition. It was found that Zn from the brass substrates is the key factor in the formation of nanowires by restricting the lateral growth of InN. The nanowire morphology is highly dependent on the growth temperature. While at a lower growth temperature, the nanowires and the In droplets have large diameters. At the elevated growth temperature, the lateral sizes of the nanowires and the In droplets are much smaller. Moreover, the nanowire diameter can be controlled in situ by varying the temperature in the growth process. This method is very instructive to the diameter-controlled growth of nanowires of other materials.

Growth kinetics and island evolution during double-pulsed molecular beam epitaxy of InN

The kinetic processes of InN growth using alternating source fluxes with sub-monolayer In pulses in plasma-assisted molecular beam epitaxy have been investigated. Growth at various temperatures reveals the existence of two growth regimes. While growth at low temperatures is solely governed by surface diffusion, a combination of decomposition, desorption, and diffusion becomes decisive at growth temperatures of 470 °C and above. At this critical temperature, the surface morphology changes from a grainy structure to a structure made of huge islands. The formation of those islands is attributed to the development of an indium adlayer, which can be observed via reflection high energy electron diffraction monitoring. Based on the growth experiments conducted at temperatures below TGrowth = 470 °C, an activation energy for diffusion of 0.54 ± 0.02 eV has been determined from the decreasing InN island density. A comparison between growth on metalorganic vapor phase epitaxy GaN templates and pseudo bulk GaN indicates that step edges and dislocations are favorable nucleation sites. Based on the results, we developed a growth model, which describes the main mechanisms of the growth.

Self-Catalyzed Growth of Vertically Aligned InN Nanorods by Metal-Organic Vapor Phase Epitaxy.

Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal-organic vapor phase epitaxy without any foreign catalyst. The In droplets on top of the nanorods indicate a self-catalytic vapor-liquid-solid growth mode. A systematic study on important growth parameters has been carried out for the optimization of nanorod morphology. The nanorod N-polarity, induced by high temperature nitridation of the sapphire substrate, is necessary to achieve vertical growth. Hydrogen, usually inapplicable during InN growth due to formation of metallic indium, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the sapphire surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temperature is similar. Transmission electron microscopy, spatially resolved energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been performed to analyze the structural properties. Spatially resolved cathodoluminescence investigations are carried out to verify the optical activity of the InN nanorods. The InN nanorods are expected to be the material of choice for high-efficiency hot carrier solar cells.

Low-temperature (≥400 °C) growth of InN by metalorganic vapor phase epitaxy using an NH3 decomposition catalyst

In this paper, we report the metalorganic vapor phase epitaxial (MOVPE) growth of InN using a NiO-based pellet-type NH3 decomposition catalyst. The use of the catalyst significantly changes the growth behavior of InN, which is dependent on the growth temperature (Tg). Continuous InN films without the incorporation of metallic In and a cubic phase are grown at Tg = 400–480 °C. An InN film grown at Tg ≈ 450 °C has a full-width at half maximum (FWHM) of 376 arcsec in the X-ray rocking curve for InN(0002) reflection. At Tg ≥ 500 °C, the deposition rate of InN rapidly decreases and the deposited films become discontinuous with large (ca. 1 µm) pyramidal grains of InN. Depositions are scarcely obtained at Tg ≥ 600 °C. Such changes in the growth behavior of InN are governed by the NH3 decomposition.

Low-temperature self-limiting atomic layer deposition of wurtzite InN on Si(100)

In this work, we report on self-limiting growth of InN thin films at substrate temperatures as low as 200 °C by hollow-cathode plasma-assisted atomic layer deposition (HCPA-ALD). The precursors used in growth experiments were trimethylindium (TMI) and N2 plasma. Process parameters including TMI pulse time, N2 plasma exposure time, purge time, and deposition temperature have been optimized for self-limiting growth of InN with in ALD window. With the increase in exposure time of N2 plasma from 40 s to 100 s at 200 °C, growth rate showed a significant decrease from 1.60 to 0.64 Å/cycle. At 200 °C, growth rate saturated as 0.64 Å/cycle for TMI dose starting from 0.07 s. Structural, optical, and morphological characterization of InN were carried out in detail. X-ray diffraction measurements revealed the hexagonal wurtzite crystalline structure of the grown InN films. Refractive index of the InN film deposited at 200 °C was found to be 2.66 at 650 nm. 48 nm-thick InN films exhibited relatively smooth surfaces with Rms surface roughness values of 0.98 nm, while the film density was extracted as 6.30 g/cm3. X-ray photoelectron spectroscopy (XPS) measurements depicted the peaks of indium, nitrogen, carbon, and oxygen on the film surface and quantitative information revealed that films are nearly stoichiometric with rather low impurity content. In3d and N1s high-resolution scans confirmed the presence of InN with peaks located at 443.5 and 396.8 eV, respectively. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) further confirmed the polycrystalline structure of InN thin films and elemental mapping revealed uniform distribution of indium and nitrogen along the scanned area of the InN film. Spectral absorption measurements exhibited an optical band edge around 1.9 eV. Our findings demonstrate that HCPA-ALD might be a promising technique to grow crystalline wurtzite InN thin films at low substrate temperatures.

Impact of substrate nitridation on the growth of InN on In2O3(111) by plasma-assisted molecular beam epitaxy

We study the growth of InN films on In2O3(111) substrates by plasma-assisted molecular beam epitaxy under N excess. InN films deposited directly on In2O3(111) exhibit a strongly faceted morphology. A nitridation step prior to growth is found to convert the In2O3(111) surface to InN{0001}. The morphology of InN films deposited on such nitridated In2O3(111) substrates is characteristic for growth by instable step-flow and is thus drastically different from the three-dimensional growth obtained without nitridation. We show that this change originates from the different polarity of the films: while InN films deposited directly on In2O3(111) are In-polar, they are N-polar when grown on the nitridated substrate.

Features of InN growth by nitrogen-plasma-assisted MBE at different ratios of fluxes of group-III and -V elements

The results of investigations of the effect of the ratios of fluxes of the Group-III and -V elements on the structural and optical properties of an InN film deposited by plasma-assisted molecular-beam epitaxy (MBE) are presented. It is shown that the InN layer consists of free-standing nanocolumns at a flux ratio of III/V < 0.6. InN growth becomes two-dimensional (2D) in the ratio range 0.6 < III/V < 0.9; however, the InN layer has a nanoporous structure. Upon passage to metal-rich conditions of growth (III/V ∼1.1), the InN layer becomes continuous. The passage from 3D to 2D growth is accompanied by an increase in the threading-dislocation density. It results in a decrease in the photoluminescence (PL) intensity of InN at room temperature. The electron concentration in the InN layers amounts to ∼5 × 1018 cm–3, which results in a shift of the PL-signal peak to the wavelength region of 1.73–1.8 μm and to a shift of the absorption edge to the region of ∼1.65 μm.

Theoretical Investigation on Structural and Electronic Properties of InN Growth on Ce-Stabilized Zirconia (111) Substrates

The structural and electronic properties of InN on Ce-stabilized zirconia (CeSZ) (111) substrates are investigated using first-principles calculations based on density functional theory with GGA +Umethod. Surface energy calculations indicate that the structure of Ce-segregated surface is more energetically stable than that of Ce-segregation-free surface. Adsorption energies of indium and nitrogen atoms on both Ce-segregated and Ce-segregation-free CeSZ (111) surfaces at the initial growth stage have been studied. The results suggest that the first layer of InN films consists of a nitrogen layer, which leads to epitaxial relationships between InN (0001) // CeSZ (111) and InN[112¯0]// CeSZ[11¯0]. In addition, density of states (DOS) analysis revealed that the hybridization effect plays a crucial role in determining the interface structure for the growth of InN on CeSZ (111) surfaces. Furthermore, adsorption energies of indium atoms on the nitrogen layer have also been evaluated in order to investigate the lattice polarity determination for InN films. It was found that an indium atom preferentially adsorbs at the center of three nitrogen atoms stacked on the CeSZ substrate, which results in the formation of In-polarity InN.

Incorporation Behaviors of In and Ga in the Two-Heater MOVPE Growth of InGaN Films

Incorporation behaviors of In and Ga of InGaN films grown by the two-heater metal-organic vapor-phase epitaxial horizontal reactor is investigated by varying growth parameters, such as the substrate temperature, ceiling temperature and reactor pressure. Two In loss mechanisms are observed by the analysis of the concentration and temperature profiles in the deposition zone. The gas-phase parasitic-loss mechanism (activation energy ∼ 34.2 ± 0.1 kcal/mol) is significant in the ceiling temperature Tceil ≥ 800°C and at substrate temperature (Tsub) of 600°C. The decomposition-loss mechanism, which arises from In desorption on the growing surface, is significant in Tsub > 625°C region. The desorption activation energy obtained is 28.0 ± 0.1 kcal/mol, which is close to that of InN (25–26 kcal/mol). This suggests the In decomposition-loss mechanism in InGaN growth does not differ substantially from that in binary InN growth. On the other hand, the gas-phase parasitic-loss mechanism of Ga is negligible in the growth condition that we have explored. Exception is found for reactor pressure at Tceil = 950°C, where both factors advantageous and disadvantageous to Ga incorporation are unambiguously observed. We have proposed explanation for the above observation.

Effect of indium accumulation on the characteristics of a-plane InN epi-films under different growth conditions

This study investigated the influence of indium accumulation happened on the surface of a-plane InN grown under different growth conditions. Three different growth rates with N/In ratio from stoichiometric to N-rich were used to grow a-plane InN epifilms on GaN-buffered r-plane sapphires by plasma-assisted molecular beam epitaxy. When a-plane InN was grown above 500°C with a high growth rate, abnormally high in-situ reflectivity was found during a-plane InN growth, which was resulted from indium accumulation on surface owing to In-N bonding difficulty on certain crystal faces of a-plane InN surface. Even using excess N-flux, indium accumulation could still be found in initial growth and formed 3-dimension-like patterns on a-plane InN surface which resulted in rough surface morphology. By reducing growth rate, surface roughness was improved because indium atoms could have more time to migrate to suitable position. Nonetheless, basal stacking fault density and crystal anisotropic property were not affected by growth rate.

MBE growth of entire-indium-composition-tunable In&amp;lt;italic&amp;gt;&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;&amp;lt;/italic&amp;gt;Ga&amp;lt;sub&amp;gt;1-&amp;lt;italic&amp;gt;x&amp;lt;/italic&amp;gt;&amp;lt;/sub&amp;gt;N alloy

As a direct band-gap semiconductor, ternary nitride alloy In x Ga1- x N has a tunable energy band-gap from 3.43 eV (for GaN) to 0.64 eV (for InN) with increasing In content, which covers the spectrum from 0.36 to 1.9 μm. In x Ga1- x N alloy has high electron drift velocity and absorption coefficient, which shows great potential application in devices such as full spectrum solar cells and light-emitting devices. Due to lack of proper substrate, In x Ga1- x N is usually grown on sapphire or GaN template. In this article, we review the growth and properties of InN and InGaN with tuable In composition grown on sapphire substrate and GaN/sapphire template by MBE. A boundary-temperature-controlled method is proposed, which successfully lead to a high-electron-mobility InN layers on sapphire substrate by MBE. The temperature-controlled epitaxy method used to grow In x Ga1- x N layers with tunable In composition on GaN/sapphire template.

High rate InN growth by two-step precursor generation hydride vapor phase epitaxy

The increase of InN growth rate by a newly developed two-step precursor generation hydride vapor phase epitaxy (HVPE) was investigated for the preparation of freestanding InN and InGaN substrates. An elevated growth rate was achieved by the complete conversion of InCl generated in the first source zone to InCl3 in the second source zone, by the supply of additional Cl2. The growth rate reached 12.4μm/h at a growth temperature of 600°C, and the rate was observed to decrease above this temperature. Specular InN layers grown at 650°C exhibited a sharp room temperature photoluminescence peak at 0.73eV with a bulk electron concentration of 1.2×1018cm−3.

Morphology evolution of nano-structured InN grown by MOMBE

In this paper, the evolution of surface morphology and electrical properties during metalorganic molecular beam epitaxy growth of InN on sapphire substrates was investigated. The growth parameters such as growth temperature, flow rate of trimethylindium (TMIn) and AlN buffer were observed to strongly correlated with InN growth. Structural property and surface morphology were analyzed by X-ray diffraction, scanning electron microscopy, atomic force microscopy and transmission electron microscopy, respectively. Electrical and transport properties were obtained by Hall-effect measurement. InN grown directly on sapphire substrate preferred two-dimensional rather than island growth at the growth temperature of 500 °C. Because of residual stress caused by lattice mismatch, however, the thickness of InN with smooth surface was limited at 50 nm. Moreover, In segregation was found under high TMIn flow rate condition. By inserting low-temperature-grown intermediate AlN buffer layer, the structural and electrical properties of InN can be effectively improved. These observations indicate that the growth parameters are essential for engineering the growth of indium nitride.

Growth of InN and In-Rich InGaN Layers on GaN Templates by Pulsed Metalorganic Chemical Vapor Deposition

InN and In-rich InGaN layers have been grown on GaN templates using the pulsed metalorganic chemical vapor deposition (MOCVD) technique and compared with analogous layers grown by conventional MOCVD. Structural investigations were performed using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Surface morphology was studied using atomic force microscopy. Electrical and optical properties were studied using Hall measurements and photoluminescence (PL) spectroscopy. All layers were free of metal droplets. InN grown using pulsed MOCVD showed fairly low background electron concentration (n e = 8 × 1018 cm−3 to 9 × 1018 cm−3) and high electron mobility (μ e = 644 cm2 V−1 s−1). Structural studies revealed increase of size (from 100 nm to 500 nm) and decrease of density of InN islands at higher growth temperatures. For In-rich InGaN layers (In content 68% and 80%) the density of islands was similar to that in InN, while the diameter varied from 50 nm to 150 nm. Inhomogeneities of In and Ga distribution in the layers resulting in broadened XRD lines and PL bands are discussed.

Growth of a-Plane InN Film and Its THz Emission

We report the growth of a-plane InN on an r-plane sapphire substrate by plasma-assisted molecular-beam epitaxy. It is found that the a-plane InN is successfully grown by using a GaN buffer layer, which has been confirmed by reflection high-energy electron diffraction, x-ray diffraction and Raman scattering measurements. The Hall effect measurement shows that the electron mobility of the as-grown a-plane InN is about 406 cm2 /V·s with a residual electron concentration of 5.7 × 10 cm−3. THz emission from the a-plane InN film is also studied, where it is found that the emission amplitude is inversely proportional to the conductivity.

Initial results for epitaxial growth of InN on gallium oxide and improved Migration-Enhanced Afterglow Epitaxy growth on gallium nitride

In this paper, the authors report on epitaxial thin InN layers grown on commercially available undoped GaN buffer layers and on Ga2O3 interlayers produced by Migration-Enhanced Afterglow Epitaxy (MEAglow). The InN layers reported here, also grown by the MEAglow technique, are 100–200 nm thick and have a measured absorption edge between 1.3 and 1.95 eV. Advancements in the growth process have now allowed the authors to improve the InN layers so that the growth has excellent two-dimensional morphology. Scanning electron microscope images show that terracing is strongly evident for samples grown on GaN templates. Atomic force microscopy shows a maximum height of the steps of about 2 nm. For the samples grown on Ga2O3, crystal quality is superior to InN grown on AlN buffers with similar thicknesses. X-ray diffraction ω-2θ measurements indicate a full width of half maximum (FWHM) of 342–389 arcseconds for these extremely thin layers; a good part of this x-ray diffraction FWHM is likely due to residual strain between the InN and GaN or between the InN and oxide.