InN Thin Films Research Articles

Layer-by-layer oxidation of InN(0001) thin films into body-center cubic In2O3(111) by cycle rapid thermal annealing

We report on a study of In2O3 thin films obtained by post-growth thermal oxidation of InN(0001) using rapid thermal annealing (RTA) and cycle-RTA (CRTA). The crystal qualities of both the resultant In2O3 and the remaining InN were significantly improved by using CRTA instead of RTA. Body-center cubic (bcc) In2O3, consisting of two In2O3(111) variants in-plane rotated 60° with respect to each other, was epitaxially grown on InN(0001). The in-plane orientations were determined as In2O3[01]//InN[110] and In2O3[01]//InN[20] for the two In2O3(111) variants. Microscopic and spectroscopic analyses, together with the effect of Si3N4 encapsulations, provide evidence that the oxidation of InN is realized by oxygen inward diffusion. The oxygen inward diffusion is slowed down and the thermal decomposition of InN is suppressed by using CRTA, which in turn leads to a layer-by-layer oxidation of InN.

Effect of In2O3Underlayer on Crystallinity of Hexagonal InN and InGaN Thin Films Grown onc-Face Sapphire Substrates

In2O3 thin films were applied as underlayers for the growth of hexagonal InN and InGaN thin films on sapphire c-face substrates. Crystallinities of the nitride thin films grown with and without the In2O3 underlayer were compared, and the effect of the underlayer on these crystallinities was investigated. The application of (111)-faced heteroepitaxial In2O3 underlayers brought clear improvement effects on the crystallinities. In2O3 can be added to one of the promising underlayer materials for the hexagonal nitride thin film growth on the c-face sapphire substrate in addition to the typical nitride buffer layer materials, such as GaN and AlN.

Effect of In2O3 Underlayer on Crystallinity of Hexagonal InN and InGaN Thin Films Grown on c-Face Sapphire Substrates

In2O3 thin films were applied as underlayers for the growth of hexagonal InN and InGaN thin films on sapphire c-face substrates. Crystallinities of the nitride thin films grown with and without the In2O3 underlayer were compared, and the effect of the underlayer on these crystallinities was investigated. The application of (111)-faced heteroepitaxial In2O3 underlayers brought clear improvement effects on the crystallinities. In2O3 can be added to one of the promising underlayer materials for the hexagonal nitride thin film growth on the c-face sapphire substrate in addition to the typical nitride buffer layer materials, such as GaN and AlN.

Decoupling single nanowire mobilities limited by surface scattering and bulk impurity scattering

We demonstrate the isolation of two free carrier scattering mechanisms as a function of radial band bending in InN nanowires via universal mobility analysis, where effective carrier mobility is measured as a function of effective electric field in a nanowire field-effect transistor. Our results show that Coulomb scattering limits effective mobility at most effective fields, while surface roughness scattering only limits mobility under very high internal electric fields. High-energy α particle irradiation is used to vary the ionized donor concentration, and the observed decrease in mobility and increase in donor concentration are compared to Hall effect results of high-quality InN thin films. Our results show that for nanowires with relatively high doping and large diameters, controlling Coulomb scattering from ionized dopants should be given precedence over surface engineering when seeking to maximize nanowire mobility.

Carrier recombination dynamics in Si doped InN thin films

Time-integrated and time-resolved photoluminescence (PL) of InN thin films of different background carrier concentrations are investigated. The PL formation mechanism is attributed to the “free-to-bound” transition by analyzing the time-integrated PL spectra at different pump fluences. The dependence of the PL decay time with emission energy is investigated using a theoretical model which speculates upon the carrier localization in InN thin films. The radiative lifetime, mobility edge, and carrier localization energy are obtained from the dependence of the PL decay time on emission energy and are studied at different background carrier concentrations. The effect of intervalley scattering between the Γ1 and Γ3 valley on the radiative lifetime, mobility edge, and carrier localization energy is discussed. The longer radiative lifetime and smaller values of the mobility edge and localization energy for 3.06 eV excitation are observed than that for the 1.53 eV excitation due to the intervalley scattering process.

InN Thin Film Lattice Dynamics by Grazing Incidence Inelastic X-Ray Scattering

Achieving comprehensive information on thin film lattice dynamics so far has eluded well established spectroscopic techniques. We demonstrate here the novel application of grazing incidence inelastic x-ray scattering combined with ab initio calculations to determine the complete elastic stiffness tensor, the acoustic and low-energy optic phonon dispersion relations of thin wurtzite indium nitride films. Indium nitride is an especially relevant example, due to the technological interest for optoelectronic and solar cell applications in combination with other group III nitrides.

Raman scattering and Rutherford backscattering studies on InN films grown by plasma-assisted molecular beam epitaxy

A series of InN thin films was grown on sapphire substrates via plasma-assisted molecular beam epitaxy (PA-MBE) with different nitrogen plasma power. Various characterization techniques, including Hall, photoluminescence, Raman scattering and Rutherford backscattering, have been employed to study these InN films. Good crystalline wurtzite structures have been identified for all PA-MBE grown InN films on sapphire substrate, which have narrower XRD wurtzite (0002) peaks, showed c-axis Raman scattering allowed longitudinal optical (LO) modes of A 1 and E 1 plus E 2 symmetry, and very weak backscattering forbidden transverse optical (TO) modes. The lower plasma power can lead to the lower carrier concentration, to have the InN film close to intrinsic material with the PL emission below 0.70 eV. With increasing the plasma power, high carrier concentration beyond 1 × 10 20 cm − 3 can be obtained, keeping good crystalline perfection. Rutherford backscattering confirmed most of InN films keeping stoichiometrical In/N ratios and only with higher plasma power of 400 W leaded to obvious surface effect and interdiffusion between the substrate and InN film.

Usage Of Porous Indium Phosphide as Substrate for Indium Nitride Films

In this paper the possibility of obtaining thin InN films on porous InP substrates by radical-beam gettering epitaxy is considered. Porous InP prepared by electrochemical etching. On the surface of porous InP by Auger spectroscopy proved the formation of films of InN.

Structural properties of InN films grown in different conditions by metalorganic vapor phase epitaxy

Abstract

A novel substrate LaBGeO5 lattice‐matched to InN

AbstractAs a novel substrate with a lattice‐mismatch of only 0.8% along the a‐axis to InN thin films, we propose LaBGeO5 (LBGO) with a trigonal symmetry for the first time. A single crystal growth of LBGO by Czochralski (Cz)‐pulling was investigated, and c‐axis‐oriented LBGO single crystals with high crystallinity were successfully grown with a pulling rate of 0.5 mm/h in O2‐atomosphere. c‐axis oriented InN film was subsequently grown on the obtained LBGO {001} substrate by metalorganic vapor epitaxy (MOVPE), and it was verified that InN film on LBGO was less‐strained as compared with that on {001} sapphire substrate. It is stressed to say that LBGO can be expected as a lattice‐matching substrate for the epitaxial growth of InN.

Electrochemical Characterization of InN Thin Films for Biosensing Applications

InN, a well-established optoelectronic material, is currently being considered as a promising material for sensor applications. In this study, the fundamental electrochemical properties of InN thin film and its potential for electrode chemical and bio-sensing applications are demonstrated. The cyclic voltammograms of different concentrations of dopamine solution in 1 M HClO4 were measured. Similarly, potentiostatic measurements at 1 V versus Ag/AgCl show stable responses and linear change of current density with concentrations up to 0.475 mM dopamine. The InN thin film also demonstrated repeatable positive photoresponse to cathodic currents in 1 mM Ru(NH3)63+ in 1M KCl solution under a 100 mW cm-2 808-nm laser light illumination at a constant -0.25 V (vs. Ag/AgCl) bias. The cathodic current response showed a 27% enhancement, demonstrating its potential as photocathode. This cathodic photocurrent behavior is explained through the electron accumulation of the InN material.

High temperature growth of InN on various substrates by plasma-assisted pulsed laser deposition

InN has attracted much attention due to its optical and electrical properties that make it suitable for the fabrication of infrared optical devices and high-speed electronic devices. In this work we report on the structural properties and morphology of InN thin films grown on different substrates by radiofrequency plasma beam assisted pulsed laser deposition. Sapphire and silicon substrates were considered for the growth of these films. The influence of substrate type and growth parameters on the morphology and structural properties of the resulting InN thin films is discussed. The structural analysis of the samples was performed by means of X-ray diffraction. The morphology of the thin films was investigated through atomic force microscopy. Although growth of InN from a metallic In target using nitrogen radiofrequency plasma assisted pulsed laser deposition was achieved for all the samples, growth conditions were found to play an important role on the crystal quality of the resulting thin films.

Growth of InN thin films on ZnO substrate by plasma-assisted molecular beam epitaxy

We have studied the microstructure property of InN epitaxial films grown on ZnO substrate by plasma-assisted molecular beam epitaxy. We found that the In 2O 3 compound was produced on ZnO substrate and many pits were formed on the InN films when InN was directly grown on ZnO substrate with the N/In flux ratio less than 40. We demonstrated that the quality of InN film was significantly improved when the In 2O 3 layer was used as a buffer to prevent the reaction between In and the ZnO substrate.

Growth Orientation Dependent Hardness for Epitaxial Wurtzite InN Films

We report the hardness of wurtzite InN thin film grown with different crystalline orientations of heteroepitaxial s-plane (1101) and a-plane (1120) on r-plane (1102) Al2O3, and homoepitaxial film on c-plane (0001) Al2O3. Hardness values along with elastic properties are studied using nanoindentation technique. Maximum hardness is reported for c-plane (approximately 8 GPa), which is followed by s-plane (approximately 5.5 GPa) and then a-plane (approximately 4 GPa) oriented InN Films. Peierls force in the slip system of different crystalline orientations for wurtzite sample is calculated for explaining the systematic variations in hardness values of these films grown with different crystalline orientations.

P‐polarized infrared attenuated total reflection study of InN thin films grown on Si(111) substrate

AbstractWe report for the first time the surface phonon polariton (SPP) and interface phonon polariton (IPP) characteristics of InN thin films grown on AlN buffer layer on Si(111) substrate by molecular beam expitaxy. The p‐polarized infrared attenuated total reflection technique was used to excite the SPP and IPP modes of the sample. It was found that the SPP mode of InN and the IPP mode of InN/AlN were clearly ob‐ served at 609 cm–1 and 877 cm–1, respectively. The origins of the observed peaks were verified by theoretical simulations based on the anisotropic model. In general, a good agreement between the experimental and theoretical results was obtained. Finally, the effect of the free carriers on the SPP mode is discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Structural Study of InN Thin Films Grown on Different Substrates by Using RF Sputtering Method

The Structural Study of InN Thin Films Grown on Different Substrates by Using RF Sputtering Method

The electrostatic coupling of longitudinal optical phonon and plasmon in wurtzite InN thin films

We utilize coherent longitudinal optical phonon as an optical nanoprobe to investigate the plasmonic behavior of wurtzite c-plane InN thin films. The transition from the three-dimensional electron gas in InN bulk toward the two-dimensional electron gas in InN thin film is revealed via measuring the coupling strength of coherent A1(LO) phonon and plasmon coupling mode. The coupling strength diminishes as the film thickness reduces and finally vanishes at 3±1 nm. This phenomenon is ascribed to the detuning of the intersubband plasmon frequency above the A1(LO) frequency, which is originated from the electronic quantum confinement in InN thin films.

Chloride ion detection by InN gated AlGaN∕GaN high electron mobility transistors

Real time chloride ion detection using InN gated AlGaN∕GaN high electron mobility transistors (HEMTs) was demonstrated. The InN thin film on the gate area of the HEMT provided fixed surface sites for reversible anion coordination. The drain current of the HEMT sensor exhibited increased a function of chloride ion concentration. The positive ions (Na+, Mg+2, and H+) in the chloride ion solutions showed no effect on the chloride ion concentration detection. The sensor was tested over a range of chloride ion concentrations from 100nMto100μM. The chloride ion HEMT sensors can be integrated with AlGaN∕GaN HEMT based pH and glucose sensors for exhaled breath condensate glucose monitoring technology. The HEMT based sensor can also be integrated into a wireless data transmission system for remote sensing applications.

InN layers grown by MOCVD on [formula omitted] substrates

Epitaxial wurtzite InN thin films have been grown by metal-organic chemical vapor deposition on (1 1 1) SrTiO 3 (STO) substrates. Interestingly, twin domain epitaxy induced by the surface reconstruction of STO is observed with the in-plane orientation relationships of [ 1 ¯ 1 0 0 ] InN ∥ [ 1 ¯ 1 0 ] STO and [ 2 1 ¯ 1 ¯ 0 ] InN ∥ [ 1 ¯ 1 0 ] STO , which is helpful to release the strain. The InN films on STO substrates exhibit a strong photoluminescence emission around 0.78 eV. Particularly, using STO substrates opens up a possibility to integrate InN with the functional oxides.

Determining surface Fermi level pinning position of InN nanowires using electrolyte gating

We demonstrate quantitative determination of surface Fermi level pinning position in InN nanowires using polymer electrolyte gating and three-dimensional (3D) electrostatic modeling of charge distribution. We find pinning of the Fermi level 0.6–0.7 eV above the conduction band minimum at the surface of the nanowires. After taking into account the Fermi level pinning, doping concentration and carrier mobilities are also evaluated and compared with InN thin films. This general approach of combining electrolyte gating experiments with 3D numerical modeling can be applied to nanowires of other materials to determine their surface Fermi level pinning position.