Triethylindium Research Articles

Analysis on Contact Resistance and Effective Channel Length of Thin Film Transistors Using Composition-Modified In–Ga–Zn-O Active Channels Prepared with Atomic Layer Deposition and Various Electrode Materials

To verify the effects of process conditions for the TFTs employing In–Ga–Zn-O (IGZO) channels prepared by atomic layer deposition (ALD), such as cationic composition of channel and/or source/drain (S/D) electrodes, the device characteristics including the field-effect mobility (μFE), the contact resistance (RC), and the channel length deviation (ΔL) were systematically investigated for the ALD IGZO thin film transistors (TFTs) fabricated with controlling the ALD subcyclic ratios and with variations in S/D electrodes of indium–tin-oxide (ITO) and molybdenum (Mo). The ALD temperature was fixed at 200 °C. When the subcyclic ratios of precursors (triethyl indium: In–Ga bimetallic: diethyl zinc) were modulated to 0:2:2, 1:2:2, and 2:2:2, the cationic compositions (In:Ga:Zn) were determined to be 1.0:2.8:5.4, 1.0:1.1:2.3, and 1.0:0.7:1.5, respectively. As the the indium (In) contents within the IGZO channel increased from 5% to 14%, the μFE’s obtained from the TFTs using ITO and Mo S/D showed dramatic improvement from 16.1 to 36.9 cm2/(V s) and 2.8 to 20.1 cm2/(V s), respectively. For both sets of devices, the ΔL’s were estimated to be sensitively varied with channel compositions, and the RC markedly decreased owing to the reduction of barrier height formed at electrode/channel interfaces with increasing the In contents. The types of S/D electrodes also have a critical effect on the device performance. The devices using Mo S/D exhibited marked degradations in device characteristics rather than the devices using ITO S/D, which was suggested to originate from the additional formation of MoO3 layer at Mo/IGZO interfaces during the ALD process for the preparation of IGZO channel layers. Based on these findings, the intrinsic values of μFE for the ALD IGZO TFTs could be determined with considerations of RC and ΔL, especially for the devices with shorter channel lengths.

Growth Temperature Influence on Atomic-Layer-Deposited In2O3 Thin Films and Their Application in Inorganic Perovskite Solar Cells.

Recently, indium oxide (In2O3) thin films have emerged as a promising electron transport layer (ETL) for perovskite solar cells; however, solution-processed In2O3 ETL suffered from poor morphology, pinholes, and required annealing at high temperatures. This research aims to carry out and prepare pinhole-free, transparent, and highly conductive In2O3 thin films via atomic layer deposition (ALD) seizing efficiently as an ETL. In order to explore the growth-temperature-dependent properties of In2O3 thin film, it was fabricated by ALD using the triethyl indium (Et3In) precursor. The detail of the ALD process at 115–250 °C was studied through the film growth rate, crystal structure, morphology, composition, and optical and electrical properties. The film growth rate increased from 0.009 nm/cycle to 0.088 nm/cycle as the growth temperature rose from 115 °C to 250 °C. The film thickness was highly uniform, and the surface roughness was below 1.6 nm. Our results confirmed that film’s structural, optical and electrical properties directly depend on film growth temperature. Film grown at ≥200 °C exhibited a polycrystalline cubic structure with almost negligible carbon impurities. Finally, the device ALD-In2O3 film deposited at 250 °C exhibited a power conversion efficiency of 10.97% superior to other conditions and general SnO2 ETL.

Properties of N-polar InGaN/GaN quantum wells grown with triethyl gallium and triethyl indium as precursors

N-polar InGaN/GaN multi quantum wells (MQWs) were grown by metal organic chemical vapor deposition (MOCVD) using a methyl-free process with triethyl gallium (TEGa) and triethyl indium (TEIn) as precursors allowing the demonstration of N-polar (In,Ga)N layers with residual carbon impurity concentrations as low as 2 × 1016 cm−3, which was about one order of magnitude lower compared to samples grown with trimethyl indium (TMIn) as the indium precursor. The residual oxygen concentration in the samples ranged between 3 and 5 × 1016 cm−3. Interestingly the significantly lower carbon content in the samples grown with TEIn resulted only in a slight increase of the quantum well luminescence compared to the samples grown with TMIn. Independent of the indium precursor used, the luminescence of the N-polar MQWs was significantly less intense compared to complimentary Ga-polar samples, which were also grown for comparison.

Indium incorporation in homoepitaxial β-Ga2O3 thin films grown by metal organic vapor phase epitaxy

Homoepitaxial β-(In,Ga)2O3 thin films were grown on (100) β-Ga2O3 substrates by metal organic vapor phase epitaxy using triethylgallium (TEGa) and triethylindium (TEIn). Deposition temperatures from 650 to 825 °C and pressures from 5 to 20 mbar have been explored. The growth rate decreased linearly with increasing deposition temperature and decreased exponentially with increasing pressure. The resulting films were characterized by atomic force microscopy (AFM), high resolution x-ray diffraction (HR-XRD), and transmission electron microscopy (TEM). As the flow rate of TEIn varied from 0 to 0.13 μmol/min during the growth, AFM showed the surface roughness of about 1 nm, while HR-XRD measurements revealed an increase of the vertical lattice spacing. The maximum atomic concentration of indium incorporated in monoclinic β-(In,Ga)2O3 is about 3.5% and shifts the optical absorption edge to lower energy by ∼0.18 eV. Further increase of the indium flow rate leads to an increase of the surface roughness and a decrease in the vertical lattice spacing due to the formation of a separate cubic In2O3 phase that was confirmed by HR-TEM images. X-ray reciprocal space maps showed that the β-(In,Ga)2O3 thin films were grown coherently on β-Ga2O3.

Indium oxide thin film prepared by low temperature atomic layer deposition using liquid precursors and ozone oxidant

Transparent conducting Indium oxide (InOx) thin films were deposited by atomic layer deposition at low deposition temperatures below 100 °C. For the comparative study with liquid precursors in low temperature thermal ALD, diethyl[1,1,1-trimethyl-N-(trimethylsilyl)silanaminato]-Indium, [3-(dimethylamino-kN)propyl-kC]dimethyl-Indium, and triethyl indium (TEIn) were used as the In precursors. Ozone was used as the oxidant for all precursors. InOx films grown using the three precursors all exhibit relatively low electrical resistivity below 10−3 Ω cm at temperatures above 150 °C. Below 100 °C, the lowest resistivity (2 × 10−3 Ω cm) was observed in the films grown with TEIn. The electrical, structural and optical properties were systematically investigated as functions of the deposition temperature and precursors.

A comparative precursor study of the growth behavior of InSb using metal-organic vapor phase epitaxy

The growth behavior of InSb using triethylantimony (TESb) in combination with either triethylindium (TEIn) or trimethylindium (TMIn) was studied. Single-phase InSb growth was only observed between 435 and 485 °C. Dependence of InSb growth rate on the substrate orientation, and an exponential dependence on the growth temperature, indicates that growth occurs in the kinetically limited regime. The In and Sb precursor mole fractions were varied to assess their effects on the growth rate. InSb growth was also studied as a function of the total reactor pressure at a constant molar flow rate, and the growth rate were found to be significantly enhanced at low reactor pressures. A growth model is proposed, which includes the reaction of parasitic adducts in the gas phase, combined with surface reactions that lead to InSb growth.

Alternative precursors for MOVPE growth of InN and GaN at low temperature

We report on the use of dimethylhydrazine (DMHy) and tertiarybuthylhydrazine (TBHy), as alternative nitrogen precursor for GaN low-temperature growth, as well as to improve the InN growth rate. Lowering the GaN growth temperature, would allow growing InN/GaN heterostructures by MOVPE, without damaging the InN layers. Increasing the low InN MOVPE growth rate is of major importance to grow reasonably thick InN layers. In this respect, triethylindium (TEIn) was also used as an alternative to trimethylindium (TMIn). We demonstrate that tertiarybutylhydrazine is a suitable nitrogen source for GaN growth at 600 °C, leading to crystalline GaN layers. These layers exhibited a peak of photoluminescence emission at 3.475 eV, at 2 K, with a narrow linewidth of 18 meV; while no detectable photoluminescence was observed for layers grown with ammonia. This result opens the way to further MOVPE growth of InN and GaN based heterostructures. The unsuccessful GaN growth in a nitrogen or argon ambient using DMHy, in contrast with hydrogen, demonstrates the active role of hydrogen in the growth process. Both DMHy and TBHy were unsuitable to grow InN, but the use of TEIn instead of TMIn together with ammonia resulted at least in doubling the InN growth rate in same growth conditions.

Growth of In<sub>2</sub>O<sub>3</sub> Thin Films on Lithium Aluminum Oxide Using a Triethylindium and Oxygen Mixture

Indium oxide (In2O3) films were successfully grown on LiAlO2 substrates using the triethylindium (TEI) as a precursor in the presence of oxygen in the metalorganic chemical vapor deposition process. We have established the correlation between the substrate temperature and the structural properties. The grain structures were clearly shown on the surface of the films deposited at 350°C. The root mean square (RMS) surface roughness of the In2O3 films increased with increasing the substrate temperature. A photoluminescence measurement at room temperature exhibited a yellow-green emission band centered at 585 nm.

Characteristics of Indium Oxide Rod-Like Structures Synthesized on Sapphire Substrates

In2O3 materials consisting of dense arrays of vertically aligned rod-like structures were deposited on sapphire substrates by thermal chemical vapor deposition (CVD) using triethylindium (TEI) and oxygen as precursors at a substrate temperature of 350 oC. The rod-like structure with a triangular cross section had a cubic structure, exhibiting preferred crystallographic orientation in the [111] direction. The photoluminescence spectra of In2O3 structures under excitation at 325 nm revealed a visible emission.

Time evolution of In2O3 rod-like structures in metalorganic chemical vapor deposition process

Transparent conduction oxide (TCO) materials exhibit high electrical conductivity, high optical transparency, and high infrared reflectivity. Among TCO materials, indium oxide (In2O3), which is an n-type semiconductor with a wide bandgap, has become the choice for many device applications [1–6]. Since low-dimensional materials have been actively investigated, stimulated by the need for understanding their novel physical and chemical properties different from those in bulk state and for their potential applications to new types of electronic, magnetic, optic, photocatalytic, and energy storage devices [7, 8], the main streams of the present studies have been focused on preparing low-dimensional crystals with special morphologies, such as nanorods, nanowires, dendrite crystals, etc. Accordingly, many means have been developed for the synthesis of the In2O3 one-dimensional (1D) structures [9–19]. In this work, in order to synthesize the In2O3 rod-like structures on silicon (Si) substrates, we have employed the metalorganic chemical vapor deposition (MOCVD) method. We have investigated the variation of the structural properties by conducting the same experiment with different growth time. The products were grown on (001)-oriented Si by MOCVD. A schematic illustration of the MOCVD system was previously reported [20, 21]. The triethylindium (TEI) with Ar carrier gas was supplied into the reactor as indium source and oxygen (O2) was used as oxidizer. The Ar carrier gas flowed through the TEI bubbler maintained at 35 ◦C. The flow rates of O2 and Ar carrier gases, respectively, were 5 standard cubic centimeters per minute (sccm) and 20 sccm, with the growth time ranging from 5 to 60 min. The substrate temperature was set to 350 ◦C. The structural properties were investigated by X-ray powder diffraction (XRD), operating on a Philips X’pert MPD X-ray diffractometer with CuKα radiation. The morphologies of the product were examined by scanning electron microscopy (SEM) (JEOL, JSM-6700F). Fig. 1 shows the cross-sectional SEM images of the products, indicating that the thicknesses of the film-like structures deposited with the growth time of 5, 10, 20, and

MOCVD route to In2O3 thin films on SiO2 substrates

Indium oxide (In2O3) film is a technologically important transparent semiconducting oxide material and thus used in various fields such as photovoltaic devices, transparent windows in liquid crystal displays, sensors, and antireflection coatings [1–3]. In2O3 films can be prepared by a wide range of deposition techniques such as evaporation [4, 5], sputtering [6–8], spray pyrolysis [9], and ultrasonic spray chemical vapor deposition (CVD) [10]. Additionally, for the metal organic CVD (MOCVD) growth, various precursors such as trimethylindium (In(CH3)3) [11, 12], indium 2,2,6,6-tetramethyl-3,5-heptanedione (In(thd)3) [11, 13], and indium acetylacetonates (In(acac)3) [14, 15] have been employed. In this letter, we report the growth of In2O3 films on SiO2 substrates using a simple reaction of a triethylindium (TEI) and oxygen (O2) mixture. We investigate the effect of deposition temperature on the structural properties of thin films. The SiO2 layer was thermally grown on the Si (0 0 1) with a thickness of 60 nm. The SiO2/Si substrate was cleaned in acetone and then rinsed by deionized water. A schematic diagram of the MOCVD reactor used in our experiments was previously reported [16]. High-purity Ar (99.999% purity) passed through the TEI bubbler and delivered TEI vapor to the reactor. The TEI bubbler was maintained at a temperature of 35 ◦C. The In2O3 film was synthesized by supplying O2 and Ar carrier gases, respectively, with the flow rate of 5 sccm (standard cubic centimeters per minute) and 20 sccm. The deposition was carried out for 20 min and the substrate temperatures used in the present work were 200, 250, and 300 ◦C. The crystalline structure of the films was examined by X-ray diffraction (XRD) analysis on the θ–2θ geometry using the CuKα line. The structural morphology was characterized by scanning electron microscopy (SEM). Fig. 1 shows the XRD spectra of the as-deposited film at substrate temperatures in the range of 200–300 ◦C. Apart from the Si(0 0 4) diffraction peak, the θ–2θ scan data from the deposits at 300 ◦C exhibit a strong and sharp peak at 30.58 ◦, corresponding to (2 2 2) diffraction peaks of cubic bixbyite In2O3 phase (JCPDS 441087). Fig. 1a indicates that although we observe a very weak (2 2 2) diffraction peak corresponding to the In2O3 structure, the film prepared at 200 ◦C is close to the amorphous phase due to the absence of a strong In2O3 diffraction peak. The (2 2 2) diffraction peak of

Adsorption and decomposition of triethylindium on an InP( [formula omitted])-(2×4) surface studied by STM, TPD, and HREELS

Adsorption and decomposition of triethylindium (TEI) on an InP(0 0 1)-(2×4) surface have been studied by scanning tunneling microscopy (STM), temperature programmed desorption (TPD), and high-resolution electron energy loss spectroscopy (HREELS). Filled-state STM images indicate that TEI molecules are preferentially adsorbed at the center of the hetero(mixed-)-dimer rows along the [1 1 ̄ 0] direction. A line profile of empty-state STM images concludes that TEI is adsorbed on the P atom at the surface. TPD data and HREELS spectra show that ethyl radical and ethylene are evolved at about 380 and 435 K, respectively, as decomposition products. The HREELS spectra suggest that TEI is adsorbed molecularly at RT and that vibration modes related to hydrocarbon disappeared at about 500 K. Adsorption sites and the decomposition mechanism are discussed in terms of the (2×4) surface structure.

Decomposition mechanism of triethylindium (TEI) on a [formula omitted] surface studied by LEED, AES, TPD and HREELS

Adsorption and decomposition of triethylindium (TEI: (C 2H 5) 3In) on a GaP(0 0 1)-(2×1) surface have been studied by low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). It is found from the TPD result that ethyl radical and ethylene are evolved at about 300–400 and 450–550 K, respectively, as decomposition products of TEI on the surface. This result is quite different from that on the GaP(0 0 1)-(2×4) surface. The activation energy of desorption of ethyl radical is estimated to be about 93 kJ/mol. It is suggested that TEI is adsorbed molecularly on the surface at 100 K and that some of TEI molecules are dissociated into C 2H 5 to form P–C 2H 5 bonds at 300 K. The vibration modes related to ethyl group are decreased in intensity at about 300–400 and 450–550 K, which is consistent with the TPD result. The TEI molecules (including mono- and di-ethylindium) are not evolved from the surface. Based on the TPD and HREELS results, the decomposition mechanism of TEI on the GaP(0 0 1)-(2×1) surface is discussed and compared with that on the (2×4) surface.

Expanded self-limiting growth condition of InP using alternate trimethylindium and tertiarybutylphosphine supply in ultrahigh vacuum

The alternate injection of trimethylindium (TMI) and tertiarybutylphosphine (TBP) without precracking was studied to expand the self-limiting growth conditions of an InP layer on InP substrates in ultrahigh vacuum. The range of growth conditions for self-limiting growth using TMI expanded two-fold compared to that using triethylindium (TEI). The carbon concentration in the InP layer grown using TMI was almost the same as that using TEI under self-limiting growth conditions. The growth rate of approximately 0.75 monolayers per cycle at the plateau was achieved on (0 0 1)-, (1 1 1)A-, and (1 1 1)B-oriented InP substrates. It was suggested that the decomposition process of TMI is identical to that of TEI, and that the growth rate with the self-limiting growth conditions results from the surface occupancy of phosphorus precursors.

Metalorganic Molecular Beam Epitaxy of CuAlSe2, CuGaSe2 and CuInSe2 on GaAs Substrate

Epitaxial layers of CuGaSe2, CuAlSe2 and CuInSe2 have been successfully grown on the GaAs(100) substrate by means of metalorganic molecular beam epitaxy (MOMBE). Cyclopentadienylcoppertriethylphosphine (CpCuTEP), triethygallium (TEGa) , triisobuthylalminium (TIBAl), triethylindium (TEIn) and selenium have been used for precursors of Cu, Ga, Al, In and Se, respectively. Epilayers have been examined by X-ray diffraction, scanning electron microscopy, electron-probe micro analysis, Raman spectroscopy, photoluminescence and photoreflectance. The c-axis -oriented epilayers exhibiting good optical properties have been grown for both CuGaSe2 and CuInSe2. In spite of the poor reproducibility of the MOMBE growth of CuAlSe2, the epitaxial layer exhibiting the edge-emission at 2.64 eV at 8 K has been grown.

Self-limiting growth conditions on (001) InP by alternate triethylindium and tertiarybutylphosphine supply in ultrahigh vacuum

Alternate injections of triethylindium (TEI) and tertiarybutylphosphine (TBP) without precracking were used to realize self-limiting growth of an InP layer on a (001) InP substrate in ultrahigh vacuum. Self-limiting growth, in which the growth rate is independent of the injection time and the pressure of TEI and TBP, was achieved at a growth temperature as low as 320 °C. The growth rate of around 0.75 ML per cycle in self-limiting growth was assumed to be due to stable surface reconstruction of (2×4)-β. A specular surface morphology was obtained in the self-limiting growth condition. By analyzing the limitation of the growth rate as well as the surface morphology of the layer, self-limiting mechanisms were proposed with respect to suppression of the TEI decomposition on the indium surface during TEI injection, suppression of the phosphorus dissociation from the InP surface during TBP evacuation, and complete reaction between TEI and TBP during TBP injection. The growth condition range for self-limiting growth was expanded with the increase in TBP dosage which was defined as the multiplication of injection time and injection pressure.

Self-limiting growth of InP by alternate trimethylindium and tertiarybutylphosphine supply in ultrahigh vacuum

The alternate injection of trimethylindium (TMI) and tertiarybutylphosphine (TBP) without precracking was studied to expand the self-limiting growth conditions of an InP layer on a (0 0 1)InP substrate in ultrahigh vacuum. Self-limiting growth, in which the growth rate is independent of the injection time and the injection pressure of TMI and TBP, was achieved at a growth temperature as low as 310°C. The range of growth conditions for self-limiting growth using TMI was expanded two-fold compared to that using triethylindium (TEI). Specular surface morphology was achieved under the self-limiting growth condition. The growth rate of around 0.7 monolayer per cycle in self-limiting growth was assumed to be due to stable surface reconstruction of (2×4)- β. It was suggested that the decomposition process of TMI is identical to that of TEI, and that β elimination does not take place in either case.

Adsorption and decomposition of triethylindium on Si(001) and GaP(001) studied by HREELS and TPD

Adsorption and decomposition of triethylindium (TEI) on Si(001) and GaP(001) surfaces have been studied by using temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). For TPD spectra of TEI on the Si(001) surface, desorption peaks are found at about 373 and 583 K for ethylene and at about 400 (broad), 773, and 923 K for hydrogen. HREELS spectra of the Si(001) surface adsorbed TEI indicate that TEI is adsorbed molecularly at 100 and 290 K and that the orientation of an In–C 2H 5 bond of TEI is near parallel to the surface above 290 K. Changes in the HREELS spectra at elevated temperatures suggest that the TPD peaks at about 373 and 583 K are due to ethylene produced by cracking TEI molecules in the mass spectrometer and by decomposition of TEI on the surface, respectively. Si–H species are suggested to be formed by decomposition of the ethyl group of TEI through a β-hydride elimination. Two peaks of hydrogen in the TPD spectra at about 773 and 923 K are discussed in terms of adsorption sites. For the GaP(001) surface, adsorbed states of TEI at 100 and 300 K are the same as for the Si(001) surface. Changes in the HREELS spectra at elevated temperatures are consistent with the previous TPD result that ethylene evolved at about 323–473 K and 523–623 K. In contrast to the result for the Si(001), the vibration mode of ν(Ga–H) is not found, which is discussed in terms of the decomposition mechanisms of TEI and Ga–H species. The ethyl group of TEI is suggested not to be switched off to the Si(001) and GaP(001) surfaces. The difference in the desorption behavior of TEI from the Si(001) and GaP(001) surfaces is discussed.

Doping of InSb and InAs using CBr 4 during growth by gas source molecular beam epitaxy

For InSb, hole concentrations up to mid-10 20 cm −3 were obtained at growth temperatures up to 450°C. This is believed to be the highest hole concentration yet reported for p-InSb. The hole concentration was found to be dependent on dopant flux and V/III ratio but not on growth temperature. Attempts to increase the hole concentration beyond this level resulted in severe degradation of the surface morphology. For InAs, all growth conditions used with elemental In produced compensated n-type material. High CBr 4 fluxes also led to severe parasitic etching. By contrast, the use of metalorganic In precursors such as triethylindium (TEI) appear to enhance the ability of carbon to incorporate on the group V rather than the group III sublattice, making the attainment of highly compensated p-type material possible, but only in a narrow range of growth conditions.

Decomposition of triethylindium (TEI) on GaP(001) surface studied by TPD, XPS and RHEED

Decomposition of triethylindium (TEI) on a GaP(001) surface with and without hydrogen gas ambience has been studied using temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED). We find TPD peaks of ethylene at about 110 and 330°C and those of hydrogen at 110, 220 and 330°C. Desorption products are not changed with and without hydrogen gas ambience. The intensity ratio of the ethylene peak at about 330 to that at 110°C increases with hydrogen gas ambience. The mechanism of decomposition of TEI on the GaP(001) surface is discussed.