Indium Nitride Layers Research Articles

On the dynamics in chemical vapor deposition of InN

Epitaxial nanometer-thin indium nitride (InN) films are considered promising active layers in various device applications but remain challenging to deposit. We compare the morphological evolution and characterizations of InN films with various growth conditions in chemical vapor deposition (CVD) by both a plasma atomic layer deposition (ALD) approach and a conventional metalorganic CVD approach. Our results show that a time-resolved precursor supply is highly beneficial for deposition of smooth and continuous InN nanometer-thin films. The time for purging the reactor between the precursor pulses and low deposition temperature are key factors to achieve homogeneous InN. The gas exchange dynamics of the reactor is further studied using computational fluid dynamics. According to our study, 320 °C is found to be the upper temperature where the dynamics of the deposition chemistry can be controlled to involve only surface reactions with surface species. The results highlight the promising role of the ALD technique in realizing electronic devices based on nanometer-thin InN layers.

InN crystal habit, structural, electrical, and optical properties affected by sapphire substrate nitridation in N-polar InN/InAlN heterostructures

Indium nitride (InN) is a very promising direct bandgap semiconductor material for near-infrared optoelectronic devices and high speed transistors, however InN growth is much more challenging compared to other III-N semiconductors. In this study we analysed the impact of pre-growth vicinal c-plane sapphire substrate nitridation on the electrical, optical, and strucutral properties of N-polar InN/InAlN heterostructures and the InN crystal habit. While a short cool-down nitridation phase resulted in a high quality InAlN layer and low quality InN layer, it was the opposite for a long cool-down nitridation phase. A trade-off between the electrical and optical properties was observed: the short nitridation cool-down produced InN layers with a higher electron mobility of 629 cm2 V−1 s−1 and low photoluminescence (PL) emission, and the long one resulted in InN with a ∼21% lower electron mobility of 497 cm2 V−1s−1 but strong PL emission. Also, a very different InN crystal habit was observed for either case. The short nitridation cool-down was conducive to the formation of a continuous layer consisting mostly of coalesced downward-pointing hexagonal pyramids, while the long one led to a layer of upward-pointing hexagonal pyramids. The local decomposition of an AlON layer produced by sapphire nitridation and variations in the InAlN surface morphology resulting in a preferential attraction of growth species and localised change in the surface free energy contributions were most likely responsible for these observations. Our results also suggest N-polar buffer layers are likely to produce coalesced InN layers with a high electron mobility, while metal-polar buffer layers may facilitate the growth of high crystal quality pyramidal InN with a strong optical response.

High-Quality, InN-Based, Saturable Absorbers for Ultrafast Laser Development

New fabrication methods are strongly demanded for the development of thin-film saturable absorbers with improved optical properties (absorption band, modulation depth, nonlinear optical response). In this sense, we investigate the performance of indium nitride (InN) epitaxial layers with low residual carrier concentration (<1018 cm−3), which results in improved performance at telecom wavelengths (1560 nm). These materials have demonstrated a huge modulation depth of 23% and a saturation fluence of 830 µJ/cm2, and a large saturable absorption around −3 × 104 cm/GW has been observed, attaining an enhanced, nonlinear change in transmittance. We have studied the use of such InN layers as semiconductor saturable absorber mirrors (SESAMs) for an erbium (Er)-doped fiber laser to perform mode-locking generation at 1560 nm. We demonstrate highly stable, ultrashort (134 fs) pulses with an energy of up to 5.6 nJ.

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.

Spontaneous Formation of Indium Clusters in InN Epilayers Grown by Molecular-Beam Epitaxy

We have studied the influence of growth conditions on the number of metallic indium clusters formed spontaneously in indium nitride (InN) layers grown by nitrogen plasma-assisted molecular-beam epitaxy (PAMBE). InN epilayers of N-and In-polarity were grown on c-sapphire substrates and GaN and AlN templates, respectively. N-polar layers were obtained in the standard PAMBE regime, while In-polar layers were grown using a three-stage regime including the stages of epitaxy with enhanced atomic migration and interruption of growth under nitrogen flow. A series of samples were prepared at various growth temperatures and relative In/N flow rates. Measurement of the magnetic-field dependences of the Hall-effect coefficient and its model approximation were used to determine the percentage content of In clusters in various InN layers and the minimum amount of such inclusions that can be achieved by varying the conditions of MBE growth.

Спонтанное формирование кластеров In в эпитаксиальных слоях InN, выращенных методом молекулярно-пучковой эпитаксии

AbstractWe have studied the influence of growth conditions on the number of metallic indium clusters formed spontaneously in indium nitride (InN) layers grown by nitrogen plasma-assisted molecular-beam epitaxy (PAMBE). InN epilayers of N-and In-polarity were grown on c-sapphire substrates and GaN and AlN templates, respectively. N-polar layers were obtained in the standard PAMBE regime, while In-polar layers were grown using a three-stage regime including the stages of epitaxy with enhanced atomic migration and interruption of growth under nitrogen flow. A series of samples were prepared at various growth temperatures and relative In/N flow rates. Measurement of the magnetic-field dependences of the Hall-effect coefficient and its model approximation were used to determine the percentage content of In clusters in various InN layers and the minimum amount of such inclusions that can be achieved by varying the conditions of MBE growth.

Morphology and Optical Properties of RF Sputtering Deposited Indium Nitride Layers Under Different N₂/Ar Ratio.

InN thin films were prepared using reactive radio frequency sputtering on (111) Si substrates under different N₂/Ar ratio. The surface morphology and optical properties of InN thin films were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscope, energy dispersive spectrometer, and UV-visible-NIR spectrophotometer at room temperature. It was found that the growth rate and surface RMS roughness of InN layers all significantly decreased with the increasing of N₂ content in the sputtering gas. All the InN films were wurtzite structure with the proportion of N₂ increasing from 40% to 100% in the mixture gas. The highly c-axis orientation InN films could only be obtained in the composition ratios of N₂ higher than 90%. The atomic percentage of N is much higher than that of In at high N₂ content films, which mainly due to the chemical reaction on the surface of Si substrate. The apparent optical band gap energy is estimated at 1.83 eV. However, the InN absorption band tail is strongly influenced by the sputtering due to a change in the species of the plasma.

Improved conversion efficiency of InN/p-GaN heterostructure solar cells with embedded InON quantum dots

An indium oxynitride (InON) quantum dot (QD) layer was inserted between the indium nitride (InN) and p-type gallium nitride (GaN) films for improving the conversion efficiency of the heterostructure solar cells. The InN/InON QD/p-GaN heterostructure solar cells exhibited a high open-circuit voltage of 2.29 V, short-circuit current density of 1.64 mA/cm2, and conversion efficiency of 1.12% under AM 1.5G illumination. Compared with samples without InON QDs, the power conversion efficiency of sample with InON QDs increased twofold; this increase was attributed to the increase in short-current density. The external quantum efficiency of 250-nm-thick InN/p-GaN heterostructure solar cells has a highest value of 6.5% in the wavelength range of 700–1100 nm. The photogenerated holes separated in the depletion region of InN thin films is difficult to transport across the energy barrier between the InN and p-GaN layers. The oxygen vacancy assisted carrier transport in the InN/InON QD/p-GaN sample, which was evidenced in its current–voltage (I–V) and capacitance–voltage (C–V) characteristics. The dark I–V characteristic curves in the bias range of −2 to 2 V exhibited ohmic behavior, which indicated the absence of a transport barrier between the InN and p-GaN layers. In addition, a shoulder peak at −0.08 V was observed in the high-frequency (60–100 kHz) C–V characteristic curves corresponding to carrier capture and emission in the shallow defect state of oxygen vacancy in the InON QDs. The oxygen vacancy exists inside the InON QDs and generates the interface states in the InON QD/p-GaN interface to form a carrier transport path. Thus, more photogenerated holes can transport via the InON QDs into the p-GaN layer, contributing to the photocurrent and resulting in high conversion efficiency for the InN/InON QD/p-GaN heterostructure solar cells.

Theoretical analysis of surface plasmon resonance based fiber optic sensor using indium nitride

An extremely sensitive surface plasmon resonance based fiber optic sensor with indium nitride (InN) layer coated on the core of the optical fiber is theoretically analyzed. The proposed sensor exhibits high sensitivity in the near infrared region of spectrum. The optimized value of thickness of InN layer is found to be 70nm. Possessing high sensitivity of 4493nm/RIU, the 70nm thick InN layer based fiber optic SPR sensor illustrates good sensing behavior.

Catalyst Temperature Dependence of NH3 Decomposition for InN Grown by Metal Organic Vapor Phase Epitaxy

In this paper, we report an independent catalyst heating system on the Pt-catalyst metal organic vapor phase epitaxy (MOVPE) for Indium nitride (InN) growth, and the dependence of the NH3 decomposition rate on the Pt catalyst temperature (RT to 1000 °C) using a quadrupole mass spectrometer (Q-MS). When the catalyst temperature is increased above the growth temperature of InN, the NH3 decomposition rate is enhanced. The grain size of InN becomes larger and the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) was drastically decreased. The increase of N atoms results in the incorporation of nitrogen into the InN layer and thus improves the crystal quality of InN. However, active H increases sharply when the catalyst heater temperature is over about 850 °C. Therefore, a great improvement in the crystal quality of InN film is expected by optimizing the growth condition including a catalyst temperature not exceeding 850 °C.

Growth of InN thin films on different Si substrates at ambient temperature

PurposeThe purpose of this paper was to investigate the growth dependence of InN on Si substrate with different orientation through RF reactive magnetron sputtering in ambient temperature.Design/methodology/approachThe authors fabricated indium nitride (InN) thin films by radio frequency (RF) sputtering. The InN thin films were deposited on Si (100), Si (110) and Si (111) substrates at room temperature. The crystalline structure and surface morphology of the InN films were characterized by X‐ray diffraction (XRD), scanning electron microscope (SEM), energy‐dispersive X‐ray spectroscopy (EDX) and atomic force microscopy (AFM).FindingsX‐ray diffraction results revealed that the wurtzite InN with preferential (101) orientation are deposited. Through the Scherrer structural analysis revealed nanocrystalline structure for InN films grown on Si (110), Si (100) and Si (111) orientation with crystallite size of 42.3, 33.8 and 24.1, respectively. The optical properties of InN layers were examined by Fourier transform infrared (FTIR) and micro‐Raman reflectance spectroscopy at room temperature. The observation of the E1(TO), A1(LO), and E2(high) phonon modes of the InN from the IR and Raman results confirmed that the deposited InN thin film has hexagonal structure.Originality/valueSi (110) surface is not isotropic and it may offer a unique orientation plane for the nitride films which could reduce the defect density and the resulting tensile stress responsible for film cracking. Therefore, it is absolutely worth exploring the growth of InN on Si (110) by using relatively simple and cheap reactive sputtering technique.

Growth of InN layers on Si (111) using ultra thin silicon nitride buffer layer by NPA-MBE

Indium nitride (InN) epilayers have been successfully grown by nitrogen-plasma-assisted molecular beam epitaxy (NPA-MBE) on Si (111) substrates using different buffer layers. Growth of a (0001)-oriented single crystalline wurtzite–InN layer was confirmed by high resolution X-ray diffraction (HRXRD). The Raman studies show the high crystalline quality and the wurtzite lattice structure of InN films on the Si substrate using different buffer layers and the InN/β–Si 3N 4 double buffer layer achieves minimum FWHM of E 2 (high) mode. The energy gap of InN films was determined by optical absorption measurement and found to be in the range of ~ 0.73–0.78 eV with a direct band nature. It is found that a double-buffer technique (InN/β–Si 3N 4) insures improved crystallinity, smooth surface and good optical properties.

Characterizations of InN Thin Films Grown on Si (110) Substrate by Reactive Sputtering

Indium nitride (InN) thin films were deposited onto Si (110) by reactive sputtering and pure In target at ambient temperature. The effects of the Ar–N2sputtering gas mixture on the structural properties of the films were investigated by using scanning electron microscope, energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray diffraction techniques. The optical properties of InN layers were examined by micro-Raman and Fourier transform infrared (FTIR) reflectance spectroscopy at room temperature. Structural analysis specified nanocrystalline structure with crystal size of 15.87 nm, 16.65 nm, and 41.64 nm for InN films grown at N2 : Ar ratio of 100 : 0, 75 : 25, and 50 : 50, respectively. The Raman spectra indicates well defined peaks at 578, 583, and 583 cm−1, which correspond to the A1(LO) phonon of the hexagonal InN films grown at gas ratios of 100 : 0, 75 : 25 and 50 : 50 N2 : Ar, respectively. Results of FTIR spectroscopy show the clearly visible TO [E1(TO)] phonon mode of the InN at 479 cm−1just for film that were deposited at 50 : 50 N2 : Ar. The X-ray diffraction results indicate that the layers consist of InN nanocrystals. The highest intensity of InN (101) peak and the best nanocrystalline InN films can be seen under the deposition condition with N2 : Ar gas mixture of 50 : 50.

Recent advances in the MOVPE growth of indium nitride

AbstractSince a few years, indium nitride promising properties for device applications have attracted much attention worldwide. Huge efforts are dedicated to optimize indium nitride growth. However, this growth is extremely challenging, in particular using the metal organic vapor phase epitaxy (MOVPE) technique which exhibits very low growth rates. This may explain why most of the samples available in the scientific community, which also present the best electrical properties, were grown by molecular beam epitaxy (MBE). However, up to date, no intrinsic indium nitride layer was obtained. InN epilayer crystalline quality suffers from the lack of lattice matched substrates, leading to the use of double‐step growth process. In this paper, we show that InN low lateral growth rate is a limiting parameter for efficient double‐step growth process. But, we also report that the use of CBrCl3 during InN growth enhances the lateral growth rate. To improve the growth rate along the c‐axis, we investigate alternative precursors for both nitrogen and indium species. We show that ammonia remains the best precursor, but combined with triethylindium, the growth rate increases with optimum crystalline quality. Finally, we compare MOVPE‐grown and MBE‐grown InN layers in order to understand the difference observed on the electrical properties. We show how thermal annealing can improve the MOVPE‐grown InN layers leading to similar electrical properties than reported in MBE‐grown samples. The role of ammonia as source of hydrogen is also discussed.

Transport characteristics of indium nitride (InN) films grown by plasma assisted molecular beam epitaxy (PAMBE)

AbstractWe report on the PAMBE‐growth of high‐quality InN layers with In polarity and on the influence of growth parameters such as Indium‐to‐nitrogen flux ratio as well as substrate temperature on the electronic transport characteristics of these layers. The flux ratio was changed between 0.94 to 1.18 near stoichiometric conditions and the growth temperature was varied between 400 and 485 °C as measured by calibrated pyrometer temperature. The InN films were grown on metal‐organic vapour deposition (MOCVD) GaN templates 3″ in diameter with InN layer thicknesses of 700 nm as determined by spectroscopic ellipsometry (SE). Under In‐rich and near stoichiometric growth conditions a minimum surface root mean square roughness of 0.6 nm was achieved. High resolution X‐ray diffraction show purely hexagonal phase growth and no evidence for the presence of cubic inclusions. InN layers grown under optimized growth conditions exhibit a narrow (FWHM 20 meV) near band edge low temperature photoluminescence (PL) spectrum with a PL peak energy of 0.67 eV, indicating an InN band gap energy of ≈ 0.7 eV, consistent with the dielectric function spectrum derived from SE measurements. Room temperature van‐der‐Pauw Hall measurements reveal high electron mobilities up to 1910 cm2/Vs with mean bulk electron concentrations as low as 5 x 1017 /cm3. Furthermore, efficient surface emission of THz radiation has been demonstrated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth study of thin indium nitride layers on InP (1 0 0) by Auger electron spectroscopy and photoluminescence

This article investigates the growth of InN layers on (100) InP in ultra-high vacuum using a glow discharge source (GDS). Auger electron spectroscopy (AES) was used to understand the different steps of the nitridation process with the analysis of In-MNN, N-KLL and P-LMM transitions. A modeling of Auger signals using a stacked layers model allows us to confirm that four monolayers of indium nitride are created on (100) InP.InN layers grown on (100) InP were studied optically by photoluminescence (PL) spectroscopy versus the excitation power and the sample temperature (10–300K). Results show broad spectral band energy close to the lowest reported InN bandgap.The temperature dependence of the PL peak energy showed a S-shaped behavior (decrease–increase–decrease). The results suggest that the InN-related emission is significantly affected by the change in carrier dynamics with increasing temperature: the effect can be due to the large exciton localization effects.

Heteroepitaxial growth of InN layers on (1 1 1) silicon substrates

Indium nitride (InN) layers were grown on (1 1 1) silicon substrates by reactive magnetron sputtering using an indium target. Atomic force microscope, X-ray diffraction, and Raman spectroscopy analysis revealed that highly c-axis preferred wurtzite InN layers with very smooth surface can be obtained on (1 1 1) silicon substrates at a substrate temperature as low as 100 °C. The results indicate that the reactive sputtering is a promising growth technique for obtaining InN layers on silicon substrates at low substrate temperature with low cost and good compatibility with microelectronic silicon-based devices.

Surface electron accumulation in indium nitride layers grown by high pressure chemical vapor deposition

Surface termination and electronic properties of InN layers grown by high pressure chemical vapor deposition have been studied by high resolution electron energy loss spectroscopy (HREELS). HREEL spectra from InN after atomic hydrogen cleaning show N–H termination with no indium overlayer or droplets and indicate that the layer is N-polar. Broad conduction band plasmon excitations are observed centered at 3400 cm −1 in HREEL spectra with 7 eV incident electron energy which shift to 3100 cm −1 when the incident electron energies are 25 eV or greater. The shift of the plasmon excitations to lower energy when electrons with larger penetration depths are used is due to a higher charge density on the surface compared with the bulk, that is, a surface electron accumulation. These results indicate that surface electron accumulation on InN does not require excess indium or In–In bonds.

Carrier concentration and surface electron accumulation in indium nitride layers grown by high pressure chemical vapor deposition

Electronic and structural properties of InN layer grown by high pressure chemical vapor deposition have been studied by high-resolution electron energy loss spectroscopy (HREELS) and room temperature infrared reflection measurements. HREEL spectra after atomic hydrogen cleaning exhibit N–H bending and stretching vibrations with no indications of an indium overlayer or droplet formation. Broad conduction band plasmon excitations are observed centered at 3100–4200cm−1 at various locations across the surface in HREEL spectra acquired with 25eV incident electron energy. The plasmon excitations are shifted about 300cm−1 higher in spectra acquired using 7eV electrons due to higher plasma frequency and carrier concentration at the surface than in the bulk which indicates surface electron accumulation. Infrared reflectance data acquired at various spots across the surface showed a similar variation in bulk plasma frequency. A three phase thin film reflection model fitted to the infrared data yielded carrier concentrations from 8.2×1019to1.5×1020cm−3 and carrier mobilities from 105 to 210cm2∕Vs.

Preparation of InN by Means of AP-HCVD Using In Buffer Layers

AbstractWe have grown indium nitride (InN) films using In buffer layer on an a-plane sapphire substrate under atmospheric pressure by halide CVD (AP-HCVD). Growth was carried out by two steps: deposition In buffer layer at 900 °C and subsequent growth of InN layer at 650 °C. In order to compare, we also grown InN films on an a-plane sapphire. The InN films are investigated on crystal quality, surface morphology and electrical property using high-resolution X-ray diffraction (HR-XRD), X-ray pole figure, scanning electron microscope (SEM), Hall measurement. The results show that the crystal quality, surface morphology and electrical property of InN films are improved by using In buffer layer.