Indium Nitride Thin Films Research Articles

Numerical simulation study on growth rate and gas reaction path of InN-MOCVD with Close-Coupled showerhead reactor

Numerical study on the influence of the carrier gas (H2 and N2), V/III ratio, inlet temperature, and pressure on gas reaction path and growth rate of indium nitride (InN) thin film in metal–organic chemical vapor deposition (MOCVD) with close-coupled showerhead (CCS) reactor was conducted. It was found that the concentrations of precursor for InN film and nanoparticle determine the growth rate and gas reaction path. InN exhibits greater difficulty in undergoing pyrolysis reactions compared to AlN and GaN. Under the conditions of this study, the gas reaction path of InN-MOCVD be dominated by adduct/amide formation path. When H2 is used as the carrier gas, the effect of H radicals on gas reactions is relatively minor, while the effect of NH2 radicals generates more nanoparticles, and significant changes in flow fields are observed compared to using N2 as the carrier gas. Under the conditions of low V/III ratio, low inlet temperature, high pressure, and low gas flow rate, the growth rate is relatively high, but the growth uniformity is decreased. There are different reasons for the effects of the above parameters, such as, altering TMIn flow to change V/III ratio and precursor concentration, varying temperature gradient due to changes in inlet temperature, and increased the particle collision frequency and residence time due to high pressure and low gas flow rate.

Study on the effect of sputtering pressure on the physical properties of InN films on ITO substrate and the dependence of carrier transport characteristics of Li-doped p-NiO/n-InN heterojunction on the environmental temperature

The exceptional performance of ITO substrate has made it possible to use indium nitride (InN) material in a variety of applications. The combination of lithium-doped NiO and n-type InN in a heterojunction shows great potential as a material for optoelectronic devices. This study investigates the influence of sputtering pressure on the crystal structure, surface morphology, optical properties, and electrical characteristics of InN thin films prepared on ITO substrates through magnetron sputtering. The research findings indicate that the InN films grow preferentially along the (002) crystal plane, with the best crystalline quality observed under a sputtering pressure of 1.5 Pa. Subsequently, the changes in the optical bandgap, transmittance, and reflectance of the InN films with varying sputtering pressure were discussed. The study also discusses a comprehensive analysis of the trends in the electrical characteristics of the InN films with sputtering pressure and environmental temperature, demonstrating their excellent thermal stability at high temperatures. Additionally, Li-doped p-NiO/n-InN heterojunction devices were fabricated and analyzed to determine the influence of environmental temperature on the carrier transport characteristics of the devices, revealing their favorable electrical properties at different temperatures. This research enriches the field of InN material studies and opens up new prospects for the performance and practical applications of InN optoelectronic devices.

Study on the preparation of InN films under different substrates and nitrogen-argon flow ratios and the effect of operating temperature on carrier transport in p-NiO/n-InN heterojunctions

In this paper, the properties of indium nitride (InN) semiconductor films deposited by magnetron sputtering were studied. The effects of different substrates (Al2O3, ITO and Si) and different nitrogen-argon flow ratios on the crystal quality of InN films were compared. The crystal structure, surface morphology, optical and electrical properties of InN films were systematically studied. The results showed that the crystallization quality of InN thin film was the best when the flow ratio of nitrogen to argon was 30/0 on Al2O3 substrate. Then the p-NiO/n-InN/AlN heterojunction device was prepared on Al2O3 by using AlN as buffer layer, and the electrical properties of the devices at different operating temperatures were analyzed. Finally, high rectification characteristics and good temperature stability were obtained. This study provides a reference for the preparation of InN films on different substrates and the application of InN-based devices.

A CFD study of the gas reaction path in growth of InN films in metal–organic chemical vapor deposition

During simulation of the growth of indium nitride (InN) thin films in metal–organic chemical vapor deposition (MOCVD), different choices of kinetic parameters (activation energy Ea and pre-exponential factor A) for gas-phase reactions give rise to many uncertainties in the gas reaction path and growth rate. This study summarized and compared the kinetic parameters of gas-phase reactions during InN MOCVD growth. The InN MOCVD growth in a close-coupled showerhead reactor was simulated with varying kinetic parameters of gas-phase reactions. The effects of kinetic parameters on the gas reaction path were determined by comparing molar concentrations and growth rates of primary In-containing substances. The results show that with varying kinetic parameters, the gas reaction path is likely to be dominated by the addition or trimethylindium pyrolysis path, or to proceed through both reaction paths. Although the reaction path changes with varying kinetic parameters, the predicted growth rates do not vary substantially, because the total rate of transport of In-containing substances to the substrate changes little with the reaction path. The results also indicate that the contribution of pyrolytic products to the growth rate is greater than that of amine, whereas H radicals have minimal effect on the gas reaction path in InN MOCVD growth.

Optical, surface, and structural studies of InN thin films grown on sapphire by molecular beam epitaxy

A series of indium nitride (InN) thin films have been grown on sapphire substrates by molecular beam epitaxy (MBE) technology under different growth conditions of temperature and plasma power. Their structural, surface, and optical properties are studied by a variety of techniques of scanning electron microscopy, Hall effect, x-ray diffraction, photoluminescence (PL), Raman scattering, x-ray photoelectron spectroscopy (XPS), synchrotron radiation x-ray absorption near edge structure (XANES), and so on. The lower carrier concentration in InN can be obtained with a higher MBE growth temperature and a lower plasma power. As the plasma power increases, the PL peak energy is observed to shift toward the higher energy side and the Raman E2 (high) and A1 (LO) modes are shifted to the lower frequency. The residual compressive strain in epitaxial InN is relaxed. The lower plasma power and the higher growth temperature are preferred for the MBE growth of high-quality InN films. The influencing factors on the InN PL peak and band gap Eg have been revealed. It is evidenced that the InN PL peak and Eg can be shifted from high down to ∼0.65 eV with the carrier concentration down to low E19 cm−3 and the plasma power down to ∼80 W. Both the XPS and N K-edge XANES revealed the antisite defect of N on the In site, NIn. The XANES In L-edge measurements on the In L3-edge of InN films with various carrier concentrations has indicated the fourfold InN intermediate crystal structures. These obtained results are significant and useful to deepen the understanding and promote further investigation in InN and III-N materials.

Understanding indium nitride thin film growth under ALD conditions by atomic scale modelling: From the bulk to the In-rich layer

In recent decades, indium nitride (InN) has been attracting a great deal of attention for its potential applicability in the field of light-emitting diodes (LEDs) and high-frequency electronics. However, the contribution from adsorption- and reaction- related processes at the atomic scale level to the InN growth has not yet been unveiled, limiting the process optimization that is essential to achieve highly crystalline and pure thin films. In this report, we investigate the reaction pathways that are involved in the crystal growth of InN thin film in atomic layer deposition (ALD) techniques from trimethylindium (TMI) and ammonia (NH3) precursors. To accomplish this task, we use a solid-state approach to perform the ab-initio calculations within the Perdew–Burke–Ernzerhof functional (PBE) level of theory. The results clarify the activation role from the N-rich layer to decrease the barrier for the first TMI precursor dissociation from Δ‡H= +227 kJ/mol, in gas phase, to solely +16 kJ/mol, in the surface environment. In either case, the subsequent CH3 release is found to be thermo- and kinetically favored with methylindium (MI) formed at the hcp site and ethane (C2H6) as the byproduct. In the following step, the TMI physisorption at a nearby occupied hcp site promotes the sequential hydrogen removal from the N-rich layer at the minimum energy cost of Δ‡H < +105 kJ/mol with methane (CH4) release. An alternative mechanism involving the production of CH4 is also feasible upon dissociation in gas phase. Furthermore, the high concentration of CH3 radicals, from precursor dissociation, might be the origin of the carbon impurities in this material under the experimental conditions of interest. Finally, the passivation methodology is not found to affect the evaluation of the surface-related processes, whereas the inclusion of spin-polarization is demonstrated to be essential to the proper understanding of the reaction mechanism.

Role of growth pressure on Structural, optical and electrical properties of indium Nitride thin films prepared by modified activated reactive evaporation

The effect of deposition conditions on the crystal structure and optical and electrical properties of Indium Nitride (InN) films deposited by modified reactive evaporation have been investigated. Substrates are kept at the electrode and thereby subjected to low-energy nitrogen ion bombardment.The effects of pressure on the structural, morphological, and optical properties of the films on Si (100) and glass substrates are investigated by X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray analysis, and UV–Vis transmittance, Photoluminescence, and Raman spectroscopy. All the films show a preferential c-axis orientation with c- lattice constant found decreasing up to 8 mTorr. The bandgap measured from the photoluminescence and optical absorption method shows similar characteristics. Raman spectra reveal broad and asymmetric line shapes for E2(high) and A1(LO) modesdue to the small phonon correlation length. The Indium oxide phase was detected for the film grown at 25 mTorr which alsodeteriorates its electrical and optical properties.

Fabrication and characterization of InN-based metal-semiconductor-metal infrared photodetectors prepared using sol–gel spin coated technique

We report on the growth and characterization of undoped indium nitride (InN) thin films grown on a silicon substrate. The InN thin films were grown on aluminium nitride (AlN) template with gallium nitride (GaN) nucleation layer using a relatively simple and low-cost sol–gel spin coating method. The crystalline structure and optical properties of the deposited films were investigated. X-ray diffraction and Raman results revealed that InN thin films with wurtzite structure were successfully grown. For InN thin film grown on a substrate with the GaN nucleation layer, its strain and dislocation density are lower than that of the substrate with the AlN nucleation layer. From the ultra-violet-visible diffuse reflectance spectrum analysis, the energy bandgap of the InN thin films with the GaN layer was 1.70 eV. The potential application of the sol–gel spin-coated InN thin films was also explored. Metal–semiconductor–metal (MSM) infrared (IR) photodetectors were fabricated by depositing the platinum contacts using two interdigitated electrodes metal mask on the samples. The finding shows that the device demonstrates good sensitivity and repeatability towards IR excitation at a wavelength of 808 nm. The photodetector characteristics at dark and photocurrent conditions such as Schottky barrier height (SBH) and ideality factor are determined. Upon exposure to the IR source at 3V applied bias, InN/AlN/Si device configuration displays rapid rise time of 0.85 s and decay time of 0.78 s, while InN/GaN/AlNSi demonstrates slow rise time of 7.45 s and decay time of 13.75 s.

Understanding Indium Nitride Thin Film Growth Under ALD Conditions by Atomic Scale Modelling: From the Bulk to the In-Rich Layer

Understanding Indium Nitride Thin Film Growth Under ALD Conditions by Atomic Scale Modelling: From the Bulk to the In-Rich Layer

Effect of N2/H2 plasma on the growth of InN thin films on sapphire by hollow-cathode plasma-assisted atomic layer deposition

In this work, we have studied the influence of N2/H2 plasma gas flow rates on the hollow-cathode plasma-assisted atomic layer deposition (HCPA-ALD) growth of indium nitride (InN) films. The influence of N2/H2 plasma gas flow rates on crystallinity, lattice distortion, phonon properties, and bandgap was analyzed. We found that the strain can be relieved fully or partially through the incorporation of H2 in plasma. We present Raman scattering measurements on HCPA-ALD grown InN films. We found that the E2-high phonon relaxation time increases with decreasing H2 plasma flow. Atomic force microscopy (AFM) topography measurements revealed high surface roughness for InN films deposited with N2/H2. The spectroscopic ellipsometry analysis revealed that InN surface layers are thick and contain large void structures with the incorporation of H2 in N2 plasma. Combining the AFM surface morphology analysis with spectroscopic ellipsometry analysis, we propose a possible surface reaction mechanism for hydrogen incorporation on an InN surface. A clear shift of the absorption edge and a decrease in the absorption coefficient were observed when H2 was introduced into N2 flow. These results may provide a useful guide for understanding the HCPA-ALD growth mechanism of InN and In-rich nitrides.

Sol–Gel Spin Coating Growth of Magnesium-Doped Indium Nitride Thin Films on Different Substrates

Sol–Gel Spin Coating Growth of Magnesium-Doped Indium Nitride Thin Films on Different Substrates

A Mixed Modified Layer Formed In Situ to Protect and Guide Lithium Plating/Stripping Behavior.

Uncontrolled lithium (Li) plating/stripping is one of the most fatal problems of lithium metal batteries (LMBs). Herein, we modified a copper (Cu) foil current collector surface with an indium nitride (InN) thin film, which regulated the Li plating/stripping process through in situ lithiation. That is, InN transformed into a lithium nitride (Li3N)/Li-In alloy phase (LixIny)-mixed protection layer during the first Li plating process. Li3N is an efficient Li+ conductor and is stable to Li, whereas LixIny possesses fast Li+ diffusion kinetics. The synergistic effect of these two species simultaneously caused the mixed protective layer to display fast Li+ diffusion, inhibited the rapid growth of Li dendrites, and induced bottom Li deposition under the protective layer. Li∥Cu cells exhibited higher Coulombic efficiency and a more stable lithium plating/stripping process than a control cell without an InN layer. Moreover, when an InN thin film was transplanted onto the surface of a Li metal sheet using the same method, the resulting Li∥Li symmetrical cell delivered extraordinary performance. This in situ formation of a multifunctional modified layer by a facile preparation process could be an effective way to inhibit dendrite growth and accelerate the application of LMBs.

Reactive Sputtering Growth of Indium Nitride Thin Films on Flexible Substrate Under Different Substrate Temperatures

Indium nitride (InN) thin films were deposited on kapton polyimide substrate by using reactive gas-timing radio frequency (RF) sputtering technique. An indium target with purity of 99.999% was used. Throughout this work, the RF power and gas ratio of argon and nitrogen were maintained at 60 W and 40:60 (Ar:N2), respectively. The substrate temperature was varied from room temperature to 300°C. The surface morphology, structural and electrical properties of the deposited thin films as a function of the substrate temperature were investigated. All the deposited InN thin films have wurtzite crystal structure with preferred orientation along the (101) direction. The InN (101) peak becomes stronger and sharper as the substrate temperature increases from 100°C to 300°C. In addition, the packing density of the grains increases as the substrate temperature increases. The deposited InN films exhibit n-type conductivity behavior and its Hall mobility increases from 720 cm2/V-s to 2670 cm2/V-s as the substrate temperature increases from room temperature to 300 °C. These results imply that nucleation and crystal growth as well as the crystalline quality were improved at higher substrate temperatures. All the results lead to conclude that the optimal substrate temperature for the deposition of InN was 300 °C.

Elucidating the role of nitrogen plasma composition in the low-temperature self-limiting growth of indium nitride thin films.

In this work, we have studied the role varying nitrogen plasma compositions play in the low-temperature plasma-assisted growth of indium nitride (InN) thin films. Films were deposited on Si (100) substrates using a plasma-enhanced atomic layer deposition (PE-ALD) reactor featuring a capacitively-coupled hollow-cathode plasma source. Trimethylindium (TMI) and variants of nitrogen plasma (N2-only, Ar/N2, and Ar/N2/H2) were used as the metal precursor and nitrogen co-reactant, respectively. In situ ellipsometry was employed to observe individual ligand exchange and plasma-assisted ligand removal events in real-time during the growth process. Only the samples grown under hydrogen-free nitrogen plasmas (Ar/N2 or N2-only) resulted in nearly stoichiometric single-phase crystalline hexagonal InN (h-InN) films at substrate temperatures higher than 200 °C under 100 W rf-plasma power. Varying the plasma gas composition by adding H2 led to rather drastic microstructural changes resulting in a cubic phase oxide (c-In2O3) film. Combining the in situ measured growth evolution with ex situ materials characterization, we propose a simplified model describing the possible surface reactions/groups during a unit PE-ALD cycle, which depicts the highly efficient oxygen incorporation in the presence of hydrogen radicals. Further structural, chemical, and optical characterization have been carried out on the optimal InN films grown with Ar/N2 plasma to extract film properties. Samples grown at lower substrate temperature (160 °C) and reduced/elevated rf-plasma power levels (50/150 W) displayed similar amorphous character, which is attributed to either insufficient surface energy or plasma-induced crystal damage. InN samples grown at 240 °C under 100 W rf-plasma showed clear polycrystalline h-InN layers with ∼20 nm average-sized single crystal domains exhibiting hexagonal symmetry.

Influence of sputtering power and Ar–N2 flow on the structure and optical properties of indium nitride films prepared by magnetron sputtering

ABSTRACTThis paper discusses the deposition of indium nitride (InN) thin films on Si (100) substrates by using pulsed DC magnetron sputtering. Effects of varying sputtering power and Ar–N2 flow ratio on the structural, morphological, and optical properties of indium nitride (InN) films were investigated. The structural characterization indicated nanocrystalline InN film with preferred orientation towards (101) plane that exhibited the optimum crystalline quality at 130 W and for 40:60 Ar–N2 ratio. The surface morphology of InN, as observed through FESEM, contained irregularly shaped nanocrystals with size that increases with higher sputtering power and Ar:N2 flow ratio. The optical properties of InN films were studied using ellipsometer at room temperature. The band gap of InN was decreased with the increase of sputtering power to 130 W, whereas an increase in the band gap was noticed with the increase of the Ar:N2 flow ratio.

Comparative Study of Gas Ratio on Indium Nitride Thin Films Grown on Flexible Substrates Prepared by Reactive Sputtering Method

In this report, indium nitride (InN) thin films were deposited on kapton polyimide flexible substrate by reactive radio frequency (RF) sputtering method using an indium target in a mixture of Ar and N2gases. The effects of the Ar:N2gas ratio on the properties of the deposited InN thin films were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and energy dispersive (EDX) spectroscopy. The XRD revealed that the deposited films composed of polycrystalline wurtzite InN. The FESEM and AFM surface morphologies showed smooth and uniform surface of gas ratio at 60:40 compare to others gas ratio. Overall, the characteristics of the InN thin films were effectively improved with combination the N2:Ar gas ration at 60:40. The results showed that the gas ratio plays an important role in improving the properties of the InN thin films.

Growth Temperature Dependence of Sol-Gel Spin Coated Indium Nitride Thin Films

The study highlights the effects of growth temperatures ranging from 500 to 650 °C on the properties of indium nitride (InN) thin films prepared by sol-gel spin coating method followed by nitridation, also, the growth mechanism was studied in depth. The findings revealed that the InN crystal growth was promoted at the growth temperature of 600 °C, by which the crystalline quality of the deposited thin films was improved and the densely packed InN grains were formed. However, thermal decomposition of InN was observed at increasing temperature to 650 °C. Apart from that, the infrared (IR) reflectance measurement shows the presence of transverse and longitudinal-optical phonon modes of wurtzite structure InN. These vibrational modes were found to be slightly shifted from the theoretical values as a result of the incorporation of oxygen contamination in the deposited thin films.

Atomic layer deposition of InN using trimethylindium and ammonia plasma

Indium nitride (InN) is a low bandgap, high electron mobility semiconductor material of interest to optoelectronics and telecommunication. Such applications require the deposition of uniform crystalline InN thin films on large area substrates, with deposition temperatures compatible with this temperature-sensitive material. As conventional chemical vapor deposition (CVD) struggles with the low temperature tolerated by the InN crystal, the authors hypothesize that a time-resolved, surface-controlled CVD route could offer a way forward for InN thin film deposition. In this work, the authors report atomic layer deposition of crystalline, wurtzite InN thin films using trimethylindium and ammonia plasma on Si(100). They found a narrow atomic layer deposition window of 240–260 °C with a deposition rate of 0.36 Å/cycle and that the flow of ammonia into the plasma is an important parameter for the crystalline quality of the film. X-ray diffraction measurements further confirmed the polycrystalline nature of InN thin films. X-ray photoelectron spectroscopy measurements show nearly stoichiometric InN with low carbon level (&amp;lt;1 at. %) and oxygen level (&amp;lt;5 at. %) in the film bulk. The low carbon level is attributed to a favorable surface chemistry enabled by the NH3 plasma. The film bulk oxygen content is attributed to oxidation upon exposure to air via grain boundary diffusion and possibly by formation of oxygen containing species in the plasma discharge.

Low temperature growth of polycrystalline InN films on non-crystalline substrates by plasma-enhanced atomic layer deposition

Indium nitride (InN) has attracted much attention due to its high electron mobility and peak electron velocity, which make it suitable for fabrication of high-speed electronic devices. In this work, we report the low temperature growth of polycrystalline InN on non-crystalline substrates by plasma-enhanced atomic layer deposition (PE-ALD). InN thin film is amorphous in nature during the initial growth stage. With the increasing growth cycles, the starting nuclei compete for space respectively and select orientations of crystal. After about 800–1200 cycles, the nuclei will grow on the suitable planes and the film turn into polycrystalline. The amorphous to polycrystalline transition of InN film is revealed definitively by the evolution of XRD patterns and the intensity of diffraction peaks with the growth cycles.

Effect of Nitrogen Gas on the Growth of Magnesium Doped Indium Nitride Thin Films via Sol-gel Spin Coating Method

The growth of magnesium doped indium nitride (InN:Mg) thin films via sol-gel spin coating method followed by nitridation process was reported in this paper. In this work, the nitridation processes were carried under ammonia with and without nitrogen ambiences. X-ray diffraction patterns reveal that InN:Mg thin film grown under nitrogen ambiences show formation of InN (101) preferential orientation wurtzite structure. Field emission scanning electron microscopy results show that both deposited films exhibit coalesced island morphology with hexagonal like structure. Energy dispersive X-ray spectroscopy revealed that sample grown under ambient with N2 gas has lower oxygen atomic percentage and higher ratio of indium to nitrogen. Two allowed Raman modes of wurtzite InN, namely, E2(High) and A1(LO) modes, were clearly detected for the deposited films under N2 gas ambient. Nevertheless, the film grown under the present of N2 gas shows an additional feature corresponding to ν4 vibration of the MgN4 tetrahedron at around 564 cm-1. The presence of this feature indicates that the magnesium acceptors were activated and the compensation of MgIn-N (LVM) was occured. Finally, all the results suggest that present of N2 gas during nitridation process will induce better grow of InN:Mg thin films.