Increasing Indium Content Research Articles

Effect of indium content on X- ray diffraction and optical constants of InxSe1-x thin films

Alloys of InxSe1-x were prepared by quenching technique withdifferent In content (x=10, 20, 30, and 40). Thin films of these alloyswere prepared using thermal evaporation technique under vacuum of10-5 mbar on glass, at room temperature R.T with differentthicknesses (t=300, 500 and 700 nm). The X–ray diffractionmeasurement for bulk InxSe1-x showed that all alloys havepolycrystalline structures and the peaks for x=10 identical with Se,while for x=20, 30 and 40 were identical with the Se and InSestandard peaks. The diffraction patterns of InxSe1-x thin film showthat with low In content (x=10, and 20) samples have semicrystalline structure, The increase of indium content to x=30decreases degree of crystallinity and further increase of indiumcontent to x=40 leads to convert structure to amorphous. Increase ofthickness from 300 to 700nm increases degree of crystallinity for allindium content. Transmittance measurements were used to calculaterefractive index n and the extinction coefficient k using Swanepole’smethod. The optical constants such as refractive index (n), extinctioncoefficient (k) and dielectric constant (εr, εi) increases for low indiumcontent samples and decreases for high indium content samples,while increase of thickness increases optical constants for all xvalues. The oscillator energy E0, dispersion energy Ed, and otherparameters have been determined by Wemple - DiDomenico singleoscillator approach.

Direct imaging of Indium-rich triangular nanoprisms self-organized formed at the edges of InGaN/GaN core-shell nanorods

Higher indium incorporation in self-organized triangular nanoprisms at the edges of InGaN/GaN core-shell nanorods is directly evidenced by spectral cathodoluminescence microscopy in a scanning transmission electron microscope. The nanoprisms are terminated by three 46 nm wide a-plane nanofacets with sharp interfaces forming a well-defined equilateral triangular base in the basal plane. Redshifted InGaN luminescence and brighter Z-contrast are resolved for these structures compared to the InGaN layers on the nanorod sidewalls, which is attributed to at least 4 % higher indium content. Detailed analysis of the inner optical and structural properties reveals luminescence contributions from 417 nm up to 500 nm peak wavelength proving the increasing indium concentration inside the nanoprism towards the nanorod surface.

Surface and optical properties of indium-rich InGaN layers grown on sapphire by migration-enhanced plasma assisted metal organic chemical vapor deposition

In-rich InGaN nanoscale thin films grown on (0001) sapphire (Al2O3) using migration enhanced plasma-assisted metal-organic chemical vapor deposition (MEPA-MOCVD) method are characterized by high-resolution x-ray diffraction (HR-XRD), x-ray photoelectron spectroscopy (XPS), Raman scattering spectroscopy (RSS), as well as variable angle spectroscopic ellipsometry (VASE). Theoretical calculations were performed to acquire the optical constants and vibrational properties of the films. The indium composition x (In) values determined by HR-XRD and from the surface area calculated by XPS are in good agreement with each other. The valence band maxima of InxGa1−xN films (x = 0.65–0.80) were observed to shift to lower binding energy with the increase of indium concentration. The RSS results confirmed the one-phonon behavior for the A1(LO) and E2(high) modes with x (In)—independent of phonon frequencies of the substrate. The simulated refractive index n was found to increase with In composition, the band gap (Eg) shifted, however, towards the lower energy side. For a given In composition and by increasing the measurement temperature from 30 °C to 600 °C, the variations of optical constants (n and Eg) showed similar trends as in samples with increasing In composition.

Investigation on Structural, Morphological, Optical and Ammonia Sensing Properties Indium Doped Nano Crystalline ZnO Thin Films Synthesized by Spray Pyrolysis Technique

In the present work, nanostructured In doped ZnO thin films were synthesized using spray pyrolysis technique with different molarity concentrations (0.001–0.004). X-ray diffraction patterns confirms the polycrystalline nature of the films with hexagonal structure. The crystallite size is going to be increases with increase in dopant concentration. The field-emission scanning electron micrograph of undoped ZnO exhibits spherical shaped particles with intergrain pores and the intergrain pores decreases with increases in indium concentration. The transmittance and band gap is going to be decreases with increase in indium concentration. The ammonia (NH3) sensing properties of the undoped ZnO and In doped ZnO thin films were carried out at room temperature and the sensing responses of the samples towards NH3 concentrations were reported.

Indium doping effect on the magnetic properties of Y-type hexaferrite Ba0.5Sr1.5Zn2(Fe1-xInx)12O22

The effect of indium doping on structural and magnetic properties of Y-type hexaferrite Ba0.5Sr1.5Zn2(Fe1-xInx)12O22 (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) prepared by the solid state reaction method was investigated. The Rietveld refinement method was used to analyze the X-ray diffraction patterns. The magnetic transition temperatures associated with the proper-screw spin phase to the collinear ferrimagnetic spin phase transition can be efficiently modulated by varying indium content. The magnetic transition temperature increases to a maximum with indium content x = 0.04 and then decreases with x, suggesting the possibility that electrically controlled magnetization reversal can be can be effectively tailored by varying indium content. The saturation magnetization at room temperature was decreased as increasing indium content, which can be explained as the metal ions occupation. It is worthy to note that the coercivity of In-doped samples was decreased drastically compared that of undoped sample, which is probably resulted from the reduction in anisotropy field with substitution of In3+ for Fe3+. The In-doped hexaferrite Ba0.5Sr1.5Zn2(Fe1-xInx)12O22 may be potential candidates for application in magnetoelectric devices.

A Theoretical Investigation of the Miscibility and Structural Properties of InxAlyGa1−x−yN Alloys

In this theoretical investigation of the miscibility in quaternary alloys, we stay in the regular solution model and determine the interaction parameters from the enthalpy of mixing calculated using a modified Stillinger–Weber (SW) potential for III‐nitride ternary alloys. From our calculation, the values of the interaction parameters are 6.605, 10.523, and 0.677 kcal mol−1, respectively, for InGaN, InAlN, and AlGaN at x = 0.5 (where x is the In and Al fraction in InGaN, InAlN, and AlGaN, respectively). These values are in good agreement with those predicted by the improved delta lattice parameter (DLP) model for nitride ternary alloys. To determine the unstable regions characterized by the spinodal decomposition of the quaternary alloy InxAlyGa1−x−yN, we consider the composition ranges of 0.06 ≤ x ≤ 1 and 0 ≤ y ≤ 0.94. Our calculations show that the phase separation temperature increases with the increase of indium concentration. For In concentration lower than 9.4%, the quaternary alloy is miscible independent of the Al and Ga compositions in the usual growth temperature range for metalorganic vapor phase epitaxy.

Effects of alloy composition and Si-doping on vacancy defect formation in (InxGa1–x)2O3 thin films

Various nominally undoped and Si-doped (InxGa1–x)2O3 thin films were grown by pulsed laser deposition in a continuous composition spread mode on c-plane α-sapphire and (100)-oriented MgO substrates. Positron annihilation spectroscopy in the Doppler broadening mode was used as the primary characterisation technique in order to investigate the effect of alloy composition and dopant atoms on the formation of vacancy-type defects. In the undoped samples, we observe a Ga2O3-like trend for low indium concentrations changing to In2O3-like behaviour along with the increase in the indium fraction. Increasing indium concentration is found to suppress defect formation in the undoped samples at [In] > 70 at. %. Si doping leads to positron saturation trapping in VIn-like defects, suggesting a vacancy concentration of at least mid-1018 cm−3 independent of the indium content.

Suppression the Leakage of Optical Field and Carriers in GaN-based Laser Diodes by using InGaN Barrier Layers

GaN-based laser diodes (LDs) with different barrier layers are investigated by using simulation and experimental methods. it is found that the absorption loss always decreases with the increasing indium content of the InGaN barrier layer in InGaN/InGaN multiquantum well (MQW) LDs, It leads to an increase of slope efficiency and output power of LDs due to the better optical confinement effect of laser beam. However, when the barrier layer changes from InGaN to AlGaN, both threshold current and slope efficiency deteriorate seriously. Except for the increase of the optical absorption loss resulting from the leakage of the optical field, a large leakage of carriers due to the increased piezoelectric polarization field in InGaN/AlGaN MQW region may also be responsible for this deterioration. Therefore, suppressing the leakage of the optical field and carriers by using relatively higher In content InGaN barrier layer is benefit for obtaining high-performance LDs with low threshold current and high output power.

Energy structure and radiative lifetimes of [formula omitted] quantum dots

We report calculations of the ground state transition energies and the radiative lifetimes in InxGa1−xN/AlN quantum dots with different size and indium content. The ground state transition energy and the radiative lifetime of the InxGa1−xN/AlN quantum dots can be varied over a wide range by changing the height of the quantum dot and the indium content. The sizes and compositions for quantum dots emitting in the wavelength range for fiber-optic telecommunications have been found. The radiative lifetime of the InxGa1−xN/AlN quantum dots increases with increase in quantum dot height at a constant indium content, and increases with increase in indium content at constant quantum dot height. For quantum dots with constant ground state transition energy the radiative lifetime decreases with increase in indium content.

Synthesis and properties of InxAlyGa1–x–yPzAs1–z/GaAs heterostructures

Phase equilibria in the In–Al–Ga–P–As system have been analyzed in terms of a simple solution model. We have calculated the stability limits of InAlGaPAs solid solutions on GaAs substrates in the temperature range 937–1223 K. The addition of indium to AlGaPAs solid solutions leads to a slight decrease in growth rate under diffusion control and a considerable increase under kinetic control. Moreover, the addition of indium to AlGaPAs solid solutions has been shown to reduce the full width at half maximum of their X-ray rocking curves and photoluminescence spectra and increase the photoluminescence intensity. Increasing the indium concentration in In x Al y Ga1–x–yP z As1–z solid solutions to x > 0.3 extends their stability region, increases their band gap, and reduces the composition region of lattice-matched In x Al y Ga1–x–yP z As1–z/GaAs heterostructures, but these become thermal expansion-matched. With increasing indium concentration in the solid solutions, the distribution coefficients of P and As decrease, whereas those of Al and In increase.

Semi-polar InGaN/GaN multiple quantum well solar cells with spectral response at up to 560 nm

We demonstrate a series of semi-polar InGaN/GaN multiple quantum well (QW) based solar cells with high indium content, where operating wavelength ranges from green to amber. These devices are grown on high crystal quality overgrown semi-polar GaN templates. The spectral response at a long wavelength of up to 560nm has been obtained. With increasing indium content of QWs (i.e., increasing operating wavelength), the external quantum efficiency increases across a wide range of wavelength. Compared to the device with green QWs, the devices with amber QWs exhibits significantly increased short-circuit current density and conversion efficiency, achieving a current density of 1.4mA/cm2 and an enhancement factor of 170% under the AM 1.5G illumination. Photoluminescence excitation measurements show that it is attributed to enhanced light absorption in InGaN QWs by pushing the QW absorption edge towards longer wavelength. Furthermore, another series of InGaN QW solar cells is investigated with different indium contents in the three QWs of each device. The device with two yellow QWs on the top and one blue QW underneath exhibits spectral response at a long wavelength of up to 560nm, whereas the device with one blue QW on the top and two yellow QWs underneath shows no response beyond 460nm. It reveals that the InGaN QW closest to the top p-type GaN plays a determined role in the spectral response on the long wavelength side.

Ultraviolet detectors based on (GaIn)_2O_3 films

We demonstrated a (GaIn)2O3 films based UV photodetector with a planar photoconductor structure, and investigated the photoresponse properties of the fabricated devices. The (GaIn)2O3 films are of ohmic contact with a Au/Ti electrode. The fabricated photodetectors show relatively high photoresponsivity of more than 0.1 A/W. The turn-on wavelength of the photodetectors varied from 285 to 315 nm with the increase of the indium content from 0.25 to 0.49. The properties of the films were also further investigated. The films are of a (−201) oriented monoclinic phase with a high transmittance of more than 90% in the visible region and smooth surfaces without phase separation. The absorption edges of the films shift toward a longer UV wavelength region with the increase of indium content. The above results suggest that wavelength selective UV detectors can be realized based on these films.

Effect of indium addition on interfacial IMC growth and bending properties of eutectic Sn–0.7Cu solder joints

The microstructure and growth behaviors of interfacial IMCs between the Sn–0.7Cu–xIn (x = 0–5.0 wt%) solder and Cu substrate under solid aging were investigated. Bending test was conducted to evaluate the mechanical properties of Cu/Sn–0.7Cu–xIn/Cu solder joints. The needle-like Cu6(Sn,In)5 IMCs formed at interface instead of Cu6Sn5 in as-soldered In-containing solder joints. During solid aging, indium addition had little influence on the growth of Cu6Sn5 IMCs, but strongly suppressed the growth of Cu3Sn IMCs. In Sn–0.7Cu–5.0In/Cu couple, the maximum solubility of indium in Cu6Sn5 and Cu3Sn was about 4.9 and 3.1 at.% respectively which was independent of aging temperature. The average composition of Cu6(Sn,In)5 and Cu3(Sn,In) were given as Cu6(Sn0.89,In0.11)5 and Cu3(Sn0.88,In0.12). After indium addition, the diffusion coefficients were found to be lower than that of Sn–0.7Cu/Cu couple and the activation energy for the growth of Cu3Sn increased with the increase of indium content. Doping indium into Sn–0.7Cu solder improved the bending properties of solder joints. Interfacial cracks were suppressed effectively after long time aging with indium addition.

Improving electrical properties of multiple dopant ZnO varistor by doping with indium and gallium

We studied the effects of indium doping on the microstructure and electrical properties of ZnO varistors co-doped with Al2O3 and Ga2O3. Scanning electron microscopy, current–voltage testing, capacitance–voltage testing, and X-ray diffraction were performed. The results showed that the leakage current of sintered varistors decreased as the indium dopant concentration was increased. The average grain size decreased slightly with increasing indium content, which improved the voltage gradient. A certain amount of the doped In3+ dissolved into the grains causing the grain resistance to decrease, which resulted in a low level residual voltage. The sintered samples with 0.024mol% indium, 0.2mol% aluminum, and 0.42mol% gallium showed excellent overall performance, exhibiting a nonlinear coefficient of 58.8, a leakage current of 1.82µA/cm2, a 1-mA residual voltage of 433.9V/mm, and a residual voltage ratio of 1.53. The obtained co-doped ZnO varistors will provide better protection and stability in applications as metal oxide arresters for power systems.

Structural impact on the nanoscale optical properties of InGaN core-shell nanorods

III-nitride core-shell nanorods are promising for the development of high efficiency light emitting diodes and novel optical devices. We reveal the nanoscale optical and structural properties of core-shell InGaN nanorods formed by combined top-down etching and regrowth to achieve non-polar sidewalls with a low density of extended defects. While the luminescence is uniform along the non-polar {1–100} sidewalls, nano-cathodoluminescence shows a sharp reduction in the luminescent intensity at the intersection of the non-polar {1–100} facets. The reduction in the luminescent intensity is accompanied by a reduction in the emission energy localised at the apex of the corners. Correlative compositional analysis reveals an increasing indium content towards the corner except at the apex itself. We propose that the observed variations in the structure and chemistry are responsible for the changes in the optical properties at the corners of the nanorods. The insights revealed by nano-cathodoluminescence will aid in the future development of higher efficiency core-shell nanorods.

Optical and microstructural properties of InGaN/GaN multiple quantum wells with embedded graphene coating

We investigate the effects of embedded graphene coating on the optical and microstructural properties of ultrathin InGaN/GaN multiple quantum wells (MQWs). The InGaN/GaN MQWs grown on graphene-buffered GaN templates displayed enhanced internal quantum efficiency compared to conventional ones and showed the internal electric field effect-free characteristic, desirable for general lighting applications. These phenomena were attributed to the enhancement of potential fluctuation with increased indium content and negligible piezoelectric polarization in ultrathin InGaN QWs, respectively. It was found that the atomically rough surface of GaN induced by embedded graphene coating efficiently relieved the biaxial compressive strain in the ultrathin InGaN/GaN QWs and enhanced the In incorporation efficiency during the InGaN growth, suggesting the potential use of atomic-thick carbon layer in niche optoelectronic applications.

Performance of InGaN based green laser diodes improved by using an asymmetric InGaN/InGaN multi-quantum well active region.

Series of green laser diodes (LDs) with different (In)GaN barrier layers are investigated. It is found that the optical confinement factor of multi-quantum well (MQW) always increases with increasing indium content of InGaN barrier layer, which results in a decrease of threshold current when indium content of InGaN barrier layer increases from 0 to 5%. However, when a high In content InGaN barrier is used (> 5%), both threshold current and slop efficiency of LDs deteriorate. It may be attributed to the waste of carriers in the potential well at the interface between the last barrier (LB) and the upper waveguide (UWG) layers, which is induced by the piezoelectric polarization effect in high In content InGaN LB layer. Therefore, a new LD structure using a thin thickness of the LB layer to reduce the effect of polarization shows a low threshold current and a high output power even when the In content of barrier layers is as large as 7%.

Correlation between indium content in monolithic InGaN/GaN multi quantum well structures on photoelectrochemical activity for water splitting

In this study, monolithic InGaN/GaN multi-quantum well structures (MQWs) were grown on sapphire substrate at various growth temperatures by metal organic chemical vapor deposition (MOCVD) method and were used for the hydrogen evolution through photoelectrochemical water splitting. The periodicity and indium concentration of monolithic InGaN/GaN MQWs, surface morphology and optical bandgap of the device structure were studied using high resolution x-ray diffraction, atomic force microscope and photoluminescence analysis respectively. The roughness and bandgap values of InGaN/GaN MQWs were found to decrease with increasing indium content. Furthermore, the influence of indium content on the photoelectrochemical hydrogen evaluation via water splitting activity of monolithic InGaN/GaN MQWs under simulated solar radiation of AM 1.5G (100 mW/cm2) were explored. The photocurrent density increased with increase of indium content due to the changes in charge transfer resistance, flat band potential and increase of donor density. The enhanced photoelectrochemical activity demonstrated by this monolithic InGaN/GaN MQWs reveals that it is suitable candidate for the light energy harvesting applications.

Study of structure and optical absorption in iso-coordinated a-InxSb20 − xAg10Se70 (0 ≤ x ≤ 20) chalcogenide films

Many physical properties the chalcogenide systems strongly depends upon the composition and type of impurity added. In this work, structural and optical properties of thermally evaporated InxSb20−xAg10Se70 (0≤x≤20) chalcogenide films were studied. Bulk polycrystalline granules were used for the deposition of thin films. XRD studies reveal the amorphous character of the as-prepared films. FESEM images reveal a change in irregular trend in the morphological structures with composition. The EDS spectra show the composition of the as-prepared films is in stoichiometric with the bulk samples. Raman Spectroscopy shows the occurrence of SbSe and SbSb bond vibrations for AgSbSe2 structural units and InSe bond vibrations in AgInSe2 structural units. The optical transmittance and reflectance measurements were used to calculate the absorption coefficient and the indirect optical band gap is found to increases with indium content. The change in film morphology and change in the concentration of molecular units have been used to discuss optical properties with the increase in indium content.

Spectroscopic investigations of polycrystalline InxSb20−xAg10Se70 (0 ⩽ × ⩽ 15) multicomponent chalcogenides

Abstract The composition dependence of physical properties of chalcogenides has recently been studied for their phase change properties and energy conversion. In the present work, we report the structure, composition, optical and Raman spectroscopy results for bulk polycrystalline InxSb20−xAg10Se70 (0 ⩽ × ⩽ 15) samples. The phase quantification and composition have been studied by using XRD and EDX techniques. The alloy composition up to 5 at.% of indium resulted in crystallization of AgSbSe2, while further increase in In content favored the formation of another chalcopyrite AgInSe2 phase yielding the solid solutions for this alloy system. A decrease in band gap up to x = 5 followed by its increase with an increase in indium concentration has been observed. The variations in shape and position of characteristic Raman bands has been used for understanding the structural modifications of the network with the variation in indium content.