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At least 19 records

Theoretical Study of Indium Compounds of Interest for Organometallic Chemical Vapor Deposition

The structural. electronic and therinochemical properties of indium compounds which are of interest in halide transport and organometallic chemical vapor deposition processes have been studied by ab initio and statistical mechanics methods. The compounds reported include: indium halides and hydrides (InF, InCl, InCl3, InH, InH2, InH3); indium clusters (In2, In3); methylindium, dimethylindium, and their hydrogen derivatives [In(CH3), In(CH3)H, In(CH3)H2, In(CH3)2, In(CH3)2H]; dimethyl-indium dimer [In2(CH3)4], trimethyl-indium [In(CH3)3]; dehydrogenated methyl, dimethyl and trimethylindium [In(CH3)2CH2, In(CH3)CH2, In(CH2)], trimethylindium adducts with ammonia, trimethylamine and hydrazine [(CH3)3In:NH3, (CH3)3In:N(CH3)3, (CH3)3In:N(H2)N(H2)]; dimethylamino-indium and methylimino-indium [In(CH3)2(NH2), In(CH3)(NH)]; indium nitride and indium nitride dimer (InN, In2N2), indium phosphide, arsenide and antimonide ([InP, InAs, InSb). The predicted electronic properties are based on density functional theory calculations; the calculated thermodynamic properties are reported following the format of the JANAF (Joint Army, Navy, NASA, Air Force) Tables. Equilibrium compositions at two temperatures (298 and 1000 K) have been analyzed for groups of competing simultaneous reactions.

Cardelino, B. H.↗

Material design of indium-based compounds: Possible candidates for charge, valence, and bond disproportionation and superconductivity

Here, we design and investigate the physical properties of new indium compounds A In X 3 ( A = alkali metals, X = F or Cl). We find nine new In-based materials in their ground state that are thermodynamically stable but are not reported in ICSD (Inorganic Crystal Structure Database). We also discuss several metastable structures. This new series of materials display multiple valences, charge and bond disproportionation, and dimerization. The most common valence of In is 3+. We also find two rare alternatives, one has In 2+ with In-In dimerization and the other shows valence disproportionation to In 1+ and In 3+ with bond disproportionation. We study the possibility of superconductivity in these new In compounds and find that CsInF 3 has a transition temperature about 24 K with sufficient hole doping and pressure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Rapid thermal annealing of indium phosphide compound semiconductors

The rapid thermal annealing (RTA) of indium phosphide (InP) substrates using a proximity contact method and silicon nitride encapsulation is investigated. The surface conditions of the InP substrates following cleaning with procedures A and B are analyzed. Procedure A involves using an iodic acid solution to remove work-damage InP surface layers and B is a degasssing process and hydrofluoric acid solution for native oxide removal. AES, XPS, and SIMS data of the proximity contact and silicon nitride encapsulated annealed samples are examined. The data reveal that RTA using proximity contact with silicon wafers does not provide adequate protection; however, the InP sample is successfully annealed when protected by a silicon nitride encapsulant.

Biedenbender, Michael D.↗

Creepy (not KREEPy) Gold-Indium Intermetallic Compounds on Secondary Ion Mass Spectrometry Samples

A series of Secondary Ion Mass Spectrometry (SIMS) sessions to measure hydrogen (H) in Martian meteorite minerals was completed using the Cameca 6f SIMS and NanoSIMS 50L at Arizona State University (ASU). During these sessions, a “creeping” phenomenon has occurred, where the edges of samples pressed in indium are covered by a metal alloy. We summarize these observations herein, present a collection of preliminary data, and discuss explanations and concerns for future SIMS work. We conclude the report with a research plan for further study.

Dudley, J. M.↗

Coincident site lattice-matched InGaN on (111) spinel substrates

Coincident site lattice-matched wurtzite (0001) In{sub 0.31}Ga{sub 0.69}N, emitting in the important green wavelength region, is demonstrated by molecular beam epitaxy on a cubic (111) MgAl{sub 2}O{sub 4} spinel substrate. The coincident site lattice matching condition involves a 30 deg. rotation between the lattice of the InGaN epitaxial layer and the lattice of the spinel. This work describes an alternative approach towards realizing more compositionally homogenous InGaN films with low dislocation density emitting in the ''green gap'' of low efficiency currently observed for semiconductor light emitting diodes (LEDs). This approach could lead to higher efficiency green LEDs presently of great interest for solid-state lighting applications.

36 MATERIALS SCIENCE↗

Regularly arranged indium islands on glass/molybdenum substrates upon femtosecond laser and physical vapor deposition processing

A bottom-up approach is presented for the production of arrays of indium islands on a molybdenum layer on glass, which can serve as micro-sized precursors for indium compounds such as copper-indium-gallium-diselenide used in photovoltaics. Femtosecond laser ablation of glass and a subsequent deposition of a molybdenum film or direct laser processing of the molybdenum film both allow the preferential nucleation and growth of indium islands at the predefined locations in a following indium-based physical vapor deposition (PVD) process. A proper choice of laser and deposition parameters ensures the controlled growth of indium islands exclusively at the laser ablated spots. Based on a statistical analysis, these results are compared to the non-structured molybdenum surface, leading to randomly grown indium islands after PVD.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Ultrahigh sensitive sub-terahertz detection by InP-based asymmetric dual-grating-gate high-electron-mobility transistors and their broadband characteristics

We report on room-temperature plasmonic detection of sub-terahertz radiation by InAlAs/InGaAs/InP high electron mobility transistors with an asymmetric dual-grating-gate structure. Maximum responsivities of 22.7 kV/W at 200 GHz and 21.5 kV/W at 292 GHz were achieved under unbiased drain-to-source condition. The minimum noise equivalent power was estimated to be 0.48 pW/Hz{sup 0.5} at 200 GHz at room temperature, which is the record-breaking value ever reported for plasmonic THz detectors. Frequency dependence of the responsivity in the frequency range of 0.2–2 THz is in good agreement with the theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Photoluminescence studies on self-organized 1.55-μm InAs/InGaAsP/InP quantum dots under hydrostatic pressure

We report an experimental study on the optical properties of the self-organized 1.55-μm InAs/InGaAsP/InP quantum dots (QDs) under hydrostatic pressure up to 9.5 GPa at 10 K. The obtained pressure coefficients of emissions from InGaAsP to InAs QDs are 92 meV/GPa and 76 meV/GPa, respectively. Their photoluminescence intensities are found to decrease significantly with increasing pressure due to the pressure-induced Γ-X mixing of InGaAsP at about 8.5 GPa. The lifetime of excitonic emission from QDs decreases from about 1.15 at zero pressure to about 1.05 ns at 7.41 GPa. The wavelength of QD emission was tuned from 1.55 to 0.9 μm by applying a pressure of 8 GPa, displaying the feasibility for indirectly characterizing the individual InAs/InGaAsP/InP QDs of 1.55-μm emission (at zero pressure) under high-pressure using silicon avalanche photodiode.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

III-V Nanowire Array Growth by Selective Area Epitaxy

III-V semiconductor nanowires are unique material phase due to their high aspect ratio, large surface area, and strong quantum confinement. This affords the opportunity to control charge transport and optical properties for electrical and photonic applications. Nanoscale selective area metalorganic chemical vapor deposition growth (NS-SAG) is a promising technique to maximize control of nanowire diameter and position, which are essential for device application. In this work, InP and GaAs nanowire arrays are grown by NS-SAG. We observe enhanced sidewall growth and array uniformity disorder in high growth rate condition. Disorder in surface morphology and array uniformity of InP nanowire array is explained by enhanced growth on the sidewall and stacking faults. We also find that AsH{sub 3} decomposition on the sidewall affects the growth behavior of GaAs nanowire arrays.

36 MATERIALS SCIENCE↗

Surface photovoltage and photoreflectance study of InGaAs/AlAsSb quantum wells

Room temperature surface photovoltage (SPV), differential surface photovoltage (DSPV), and photoreflectance (PR) measurements were performed on InGaAs/AlAsSb QWs grown on InP substrates. Clear and well-resolved structures, which could be attributed to the interband optical transitions originating in the QWs, were observed in every spectrum. Transition energies measured from the SPV, DSPV, and PR spectra correspond well with those theoretically calculated from the confined energy levels in the QWs. Features those can be attributed to the transitions at the AlAsSb to InP hetero-interfaces were observed in the SPV and DSPV spectra.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well

We have investigated the carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well (QW) by time-resolved photoluminescence (PL) measurement. The sample consists of an 8-nm-thick GaIn{sub 0.36}N{sub 0.006}AsSb{sub 0.015} well, 5-nm-thick GaN{sub 0.01}AsSb{sub 0.11} intermediate barriers and 100-nm-thick GaAs barriers grown by molecular beam epitaxy on a GaAs(100) substrate. The spin relaxation time and recombination lifetime at 10 K are measured to be 228 ps and 151 ps, respectively. As a reference, we have also obtained a spin relaxation time of 125 ps and a recombination lifetime of 63 ps for GaInNAs/GaNAs/GaAs QW. This result shows that crystal quality is slightly improved by adding Sb, although these short carrier lifetimes mainly originate from a nonradiative recombination. These spin relaxation times are longer than the 36 ps spin relaxation time of InGaAs/InP QWs and shorter than the 2 ns spin relaxation time of GaInNAs/GaAs QW.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Enhanced room temperature electronic and thermoelectric properties of the dilute bismuthide InGaBiAs

We report room temperature electronic and thermoelectric properties of Si-doped In{sub 0.52}Ga{sub 0.48}Bi{sub y}As{sub 1-y} with varying Bi concentrations. These films were grown epitaxially on a semi-insulating InP substrate by molecular beam epitaxy. We show that low Bi concentrations are optimal in improving the conductivity, Seebeck coefficient, and thermoelectric power factor, possibly due to the surfactant effects of bismuth. We observed a reduction in thermal conductivity with increasing Bi concentration, which is expected because of alloy scattering. We report a peak ZT of 0.23 at 300 K.

36 MATERIALS SCIENCE↗

SiN{sub x}-induced intermixing in AlInGaAs/InP quantum well through interdiffusion of group III atoms

We analyze the composition profiles within intermixed and non-intermixed AlInGaAs-based multiple quantum wells structures by secondary ion mass spectrometry and observe that the band gap blue shift is mainly attributed to the interdiffusion of In and Ga atoms between the quantum wells and the barriers. Based on these results, several AlInGaAs-based single quantum well (SQW) structures with various compressive strain (CS) levels were grown and their photoluminescence spectra were investigated after the intermixing process involving the encapsulation of thin SiN{sub x} dielectric films on the surface followed by rapid thermal annealing. In addition to the annealing temperature, we report that the band gap shift can be also enhanced by increasing the CS level in the SQW. For instance, at an annealing temperature of 850 Degree-Sign C, the photoluminescence blue shift is found to reach more than 110 nm for the sample with 1.2%-CS SQW, but only 35 nm with 0.4%-CS SQW. We expect that this relatively larger atomic compositional gradient of In (and Ga) between the compressively strained quantum well and the barrier can facilitate the atomic interdiffusion and it thus leads to the larger band gap shift.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Single photon emission at 1.55 μm from charged and neutral exciton confined in a single quantum dash

We investigate charged and neutral exciton complexes confined in a single self-assembled InAs/InGaAlAs/InP quantum dash emitting at 1.55 μm. The emission characteristics have been probed by measuring high-spatial-resolution polarization-resolved photoluminescence and cross-correlations of photon emission statistics at T = 5 K. The photon auto-correlation histogram of the emission from both the neutral and charged exciton indicates a clear antibunching dip with as-measured g{sup (2)}(0) values of 0.18 and 0.31, respectively. It proves that these exciton complexes confined in single quantum dashes of InP-based material system can act as true single photon emitters being compatible with standard long-distance fiber communication technology.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

A Study of the Growth of Single Crystals

Research on the growth of single crystals of the III-V compound indium antimonide was pursued in order to gain a firsthand knowledge of some factors which govern the growth of single crystals of this compound. These studies were conducted using a standard Czochralski crystal pulling furnace. This type of furnace allows crystals to be formed without being constrained to a crucible. Several factors were found to have a large detrimental effect on the growth of single crystals of indium antimonide, the most important of which seems to be the degree to which the environment surrounding the crystal during growth can be controlled. Ways to overcome these effects were determined and are outlined.

Desmet, D. J.↗

Compositionally controlled metal-insulator transition in Tl{sub 2-x}In{sub x}TeO{sub 6}

Tl{sub 2}TeO{sub 6} and In{sub 2}TeO{sub 6} are both known to crystallize in the Na{sub 2}SiF{sub 6}-type structure. We find Tl{sub 2}TeO{sub 6} is metallic, whereas In{sub 2}TeO{sub 6} is an insulator. We have prepared a complete Tl{sub 2-x}In{sub x}TeO{sub 6} series in a search for a compositionally controlled metal-insulator transition that might be expected if a complete solid solution can be obtained. Unit cell edges and volume vary monotonically with no indication of a miscibility gap. The metal-insulator transition occurs at an x value of about 1.4, which can be rationalized on a percolation model. No superconductivity could be detected down to 5 K. -- Graphical abstract: A complete solid solution between Tl{sub 2}TeO{sub 6} and In{sub 2}TeO{sub 6} is formed. A compositionally controlled metal-insulator transition occurs in Tl{sub 2-x}In{sub x}TeO{sub 6} at an x value of about 1.5. No superconductivity could be detected down to 5 K. Display Omitted Research highlights: {yields} A complete solid solution between Tl{sub 2}TeO{sub 6} and In{sub 2}TeO{sub 6} is formed. {yields} A compositionally controlled metal-insulator transition occurs in Tl{sub 2-x}In{sub x}TeO{sub 6} at an x value of about 1.5, which can be rationalized on a percolation model. {yields} No superconductivity could be detected down to 5 K.

36 MATERIALS SCIENCE↗

Dependence of selectivity on plasma conditions in selective etching in submicrometer pitch grating on InP surface by CH{sub 4}/H{sub 2} reactive ion etching

We studied selective etching and polymer deposition in submicrometer pitch gratings on the surface of InP using reactive ion etching with methane and hydrogen and investigated the plasma condition dependence of the selectivity. Using a mask structure consisting of regions with and without a thick layer on a grating-patterned thin layer, we achieved selective etching in submicrometer pitch gratings. In experiments conducted on the same surface at the same time, the InP is selectively etched in the window of the grating in the region with the thick layer, but it is not etched, and polymer is deposited, in the window of the grating in the region without the thick layer. We found that the selectivity depends on the plasma conditions, such as the hydrogen flow rate, pressure, and plasma power in reactive ion etching. This dependence might result from the variation in the ionic atoms of hydrogen or hydrocarbon/hydrogen, which are attracted to the charged mask and supplied to the window of the grating.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Very low resistance alloyed Ni-based ohmic contacts to InP-capped and uncapped n{sup +}-In{sub 0.53} Ga{sub 0.47}As

Successful application of the silicide-like Ni{sub x}InGaAs phase for self-aligned source/drain contacts requires the formation of low-resistance ohmic contacts between the phase and underlying InGaAs. We report Ni-based contacts to InP-capped and uncapped n{sup +}- In{sub 0.53}Ga{sub 0.47}As (N{sub D} = 3 × 10{sup 19 }cm{sup −3}) with a specific contact resistance (ρ{sub c}) of 4.0 × 10{sup −8 }± 7 × 10{sup −9} Ω·cm{sup 2} and 4.6 × 10{sup −8 }± 9 × 10{sup −9} Ω·cm{sup 2}, respectively, after annealing at 350 °C for 60 s. With an ammonium sulfide pre-metallization surface treatment, ρ{sub c} is further reduced to 2.1 × 10{sup −8 }± 2 × 10{sup −9} Ω·cm{sup 2} and 1.8 × 10{sup −8 }± 1 × 10{sup −9} Ω·cm{sup 2} on epilayers with and without 10 nm InP caps, respectively. Transmission electron microscopy reveals that the ammonium sulfide surface treatment results in more complete elimination of the semiconductor's native oxide at the contact interface, which is responsible for a reduced contact resistance both before and after annealing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗