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8 Feb 1999

Volume 74, Issue 6, pp. 777-892

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Piezoelectric effects in the optical properties of strained InGaN quantum wells

L.-H. Peng, C.-W. Chuang, and L.-H. Lou

Appl. Phys. Lett. 74, 795 (1999); http://dx.doi.org/10.1063/1.123370 (3 pages) | Cited 41 times

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We investigated the carrier-injection effects in the emission spectrum of strained GaN/InGaN/AlGaN quantum well (QW) blue emitters using a pulsed current excitation technique. Spectral blueshift as large as 80 meV in the emission peak energy was observed as the injection current increases from 1 mA to 1 A. Based on a self-consistent calculation that couples the Poisson equation with a wurtzite-type Rashba–Sheka–Pikus Hamiltonian, four important interactions are evaluated in order to determine the optical properties of InGaN QW. It is shown that the spectral redshifting caused by a piezoelectricity induced quantum confined Stark effect and carrier-induced band gap renormalization is counteracted by a blueshift due to the band filling and charge screening effects. The increase of InGaN QW emission peak energy and intensity with injected carriers suggests a dominant contribution from the latter in a band-to-band recombination process. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Jq Electro-optical effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.60.Fi Electroluminescence
77.65.-j Piezoelectricity and electromechanical effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
02.30.Jr Partial differential equations
02.60.Lj Ordinary and partial differential equations; boundary value problems

Erbium (III) tris(8-hydroxyquinoline) (ErQ): A potential material for silicon compatible 1.5 μm emitters

W. P. Gillin and R. J. Curry

Appl. Phys. Lett. 74, 798 (1999); http://dx.doi.org/10.1063/1.123371 (2 pages) | Cited 70 times

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Samples of erbium (III) tris(8-hydroxyquinoline) (ErQ) have been prepared and their photoluminescence measured. Clearly resolved peaks due to intra-atomic transitions between the 4I13/2 and 4I15/2 levels can be observed at room temperature. The possibility of depositing ErQ on to silicon to produce organic electroluminescent diodes offers the possibility of a cheap 1.5 μm emitter based on silicon technology. © 1999 American Institute of Physics.
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78.55.Kz Solid organic materials
85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics

Microstructural study of a C–Fe alloy synthesized by ion-beam sputtering co-deposition

David Babonneau, Thierry Cabioc’h, Marie-Françoise Denanot, and André Naudon

Appl. Phys. Lett. 74, 800 (1999); http://dx.doi.org/10.1063/1.123372 (3 pages) | Cited 9 times

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A carbon–iron thin film, composition 46 at. % Fe and thickness 26 nm, was synthesized by ion-beam sputtering with a substrate temperature of 573 K. The microstructure of the film was characterized by transmission electron microscopy and small-angle x-ray scattering under grazing incidence. It consisted of iron-rich particles, with an average in-plane diameter of 3.2 nm, uniformly dispersed in a graphite-like carbon matrix. These particles were elongated along the in-depth direction, that of the thin-film growth. After annealing at 623 K for 1 h, no modification in the microstructure of the film was observed. The present study shows that the co-sputtering of graphite and iron performed at low temperature in comparison with the conventional arc discharge method, is a useful synthesis method to obtain thin films of encapsulated nanoparticles which have a good thermal stability. © 1999 American Institute of Physics.
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81.05.Bx Metals, semimetals, and alloys
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
68.60.Dv Thermal stability; thermal effects
78.70.Ck X-ray scattering
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization

Cell gap margin enlargement of in-plane switching mode liquid crystal displays using weak-anchoring effects

Makoto Yoneya, Kishirou Iwasaki, Yasushi Tomioka, and Katsumi Kondo

Appl. Phys. Lett. 74, 803 (1999); http://dx.doi.org/10.1063/1.123373 (3 pages) | Cited 8 times

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A method to enlarge the allowable range of marginal variation of the cell gap to ensure uniform brightness of in-plane switching mode liquid crystal displays is proposed. The proposed method is based on enlargement of the effective cell gap using the extrapolation length that is generated with weak-anchoring effects at liquid crystal/alignment layer interfaces. The method is evaluated with simulations and experiments. The results support the effectiveness of the method. © 1999 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Ultrathin silicon oxynitride film formation by plasma immersion nitrogen implantation

I. J. R. Baumvol, C. Krug, F. C. Stedile, M. L. Green, D. C. Jacobson, D. Eaglesham, J. D. Bernstein, J. Shao, A. S. Denholm, and P. L. Kellerman

Appl. Phys. Lett. 74, 806 (1999); http://dx.doi.org/10.1063/1.123374 (3 pages) | Cited 8 times

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A method is proposed to prepare ultrathin silicon oxynitride films for gate dielectrics used in deep submicron metal–oxide–semiconductor field effect transistor device structures, namely plasma immersion N implantation into SiO2 films. Plasma immersion implantation pulse voltages in the range 200–1000 V, and fluences from 1016 to 1017 N cm−2 were implanted into thermally grown SiO2 films, with thicknesses between 3 and 6 nm. The areal densities of N and O in the resulting oxynitride films were determined by nuclear reaction analysis, before and after annealing in high-vacuum. N, O, and Si profiles in the films were determined with subnanometric depth resolution by medium energy ion scattering. The results indicate that plasma immersion ion implantation allows for shallow and controlled deposition of significant amounts of nitrogen (up to 3.8 nm of equivalent Si3N4 thickness). Implantation is accompanied by moderate damage at the oxynitride/Si interface which can be recovered by thermal annealing. © 1999 American Institute of Physics.
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85.40.Ry Impurity doping, diffusion and ion implantation technology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing
68.55.Nq Composition and phase identification
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Field-enhanced emission rate and electronic properties of a defect introduced in n-GaN by 5.4 MeV He-ion irradiation

S. A. Goodman, F. D. Auret, F. K. Koschnick, J.-M. Spaeth, B. Beaumont, and P. Gibart

Appl. Phys. Lett. 74, 809 (1999); http://dx.doi.org/10.1063/1.123375 (3 pages) | Cited 12 times

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A deep level defect ER3, introduced in n-GaN by high energy (5.4 MeV) He ions, was characterized by deep level transient spectroscopy (DLTS). This defect, 0.196±0.004 eV below the conduction band, with an apparent capture cross-section of 3.5±1×10−15 cm2, is introduced uniformly in the region profiled by DLTS at a rate of 3270±200 cm−1. The emission rate of this defect depends on the electric field strength in the space-charge region. This emission rate is modeled according to the Poole–Frenkel distortion of a square well with a radius of 20±2 Å or alternatively, a Gaussian well with a characteristic width of 6.0±1 Å. Hence, we conclude that ER3 is a point defect which has a field dependence not explained by the classical Poole–Frenkel enhancement. © 1999 American Institute of Physics.
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71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
73.50.Fq High-field and nonlinear effects
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects

Impurity oxygen redistribution in a nanocrystallized Zr65Cr15Al10Pd10 metallic glass

M. W. Chen, A. Inoue, T. Sakurai, D. H. Ping, and K. Hono

Appl. Phys. Lett. 74, 812 (1999); http://dx.doi.org/10.1063/1.123376 (3 pages) | Cited 17 times

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We report atom probe results on impurity oxygen dissolution in a Zr65Cu15Al10Pd10 metallic glass and its redistribution during nanocrystallization. Approximately 0.1 at. % impurity oxygen is detected from the as-melt-spun Zr65Cu15Al10Pd10 metallic glass. Oxygen redistribution occurs during annealing. In some crystallites, oxygen up to 4 at. % is detected, and virtually no oxygen is dissolved in the remaining amorphous phase. This result directly demonstrates that impurity oxygen promotes the crystallization by forming metastable phases containing high content oxygen and thereby influences the kinetics of crystallization. © 1999 American Institute of Physics.
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61.43.Fs Glasses
61.46.-w Structure of nanoscale materials
64.75.-g Phase equilibria
81.05.Kf Glasses (including metallic glasses)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Bx Metals, semimetals, and alloys
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Aligned island formation using an array of step bands and holes on Si(111)

Yoshikazu Homma, Paul Finnie, and Toshio Ogino

Appl. Phys. Lett. 74, 815 (1999); http://dx.doi.org/10.1063/1.123377 (3 pages) | Cited 15 times

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We investigated the control of island formation using a patterned Si(111) surface with a periodic array of holes. During annealing, Au and Ga form islands at fixed locations on the array of step bands surrounding the holes. These materials or their silicides are in liquid phase at elevated temperatures. They diffuse along the step bands and accumulate at particular points on the periodic step bands. The size of the islands can be precisely designed by controlling the size of the pattern. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
73.20.At Surface states, band structure, electron density of states
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing

Strong influence of SiO2 thin film on properties of GaN epilayers

X. C. Wang, S. J. Xu, S. J. Chua, K. Li, X. H. Zhang, Z. H. Zhang, K. B. Chong, and X. Zhang

Appl. Phys. Lett. 74, 818 (1999); http://dx.doi.org/10.1063/1.123378 (3 pages) | Cited 9 times

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In this letter, we report strong degradation of photoluminescence (PL) performance of GaN epilayers due to SiO2 layers that were deposited on GaN surfaces by electron-beam evaporation. Secondary ion mass spectrometry measurements show that the oxygen concentration of GaN with SiO2 layers is one order of magnitude more than that of as-grown GaN. This fact indicates that oxygen can very easily replace nitrogen in GaN. It was also found that rapid thermal processing can recover and improve the optical quality of GaN with SiO2 layer. As a reference, SixNy was found to have little effect on PL performance of GaN. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.55.-a Thin film structure and morphology
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Ballistic phonon transmission across wafer-bonded crystals

M. E. Msall, A. Klimashov, S. Kronmüller, H. Kostial, W. Dietsche, and K. Friedland

Appl. Phys. Lett. 74, 821 (1999); http://dx.doi.org/10.1063/1.123379 (3 pages) | Cited 2 times

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We have studied phonon transmission through wafer-bonded GaAs–GaAs interfaces using the techniques of phonon imaging. The short wavelength phonons used for imaging (λ ≈ 10 nm) are an extremely sensitive probe of the bond. We report unprecedented transmission of phonons through carefully prepared bonds. This transmission is remarkable since strong phonon scattering is usually observed at virtually any free surface. The dramatic differences between phonon transmission through well bonded interfaces and phonon transmission through poorly bonded interfaces are the basis of an easily determined quality factor of the bond. In contrast to electron microscopy, the phonon measurements of bond quality are not destructive. © 1999 American Institute of Physics.
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68.35.Ja Surface and interface dynamics and vibrations
81.05.Ea III-V semiconductors

Ultrathin and highly insulating amorphous-Ta2O5 films formed on Ru/TiN/Ti/n+-Si substrates

B. K. Moon, J. Aoyama, and K. Katori

Appl. Phys. Lett. 74, 824 (1999); http://dx.doi.org/10.1063/1.123380 (3 pages) | Cited 8 times

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This letter reports on highly insulating amorphous-Ta2O5 (a-Ta2O5) films with ultrathin SiO2 effective thickness [teff(SiO2)]. Insulating properties were improved using dry-O3 annealing at 450 °C, in which the typical leakage current density and resistivity at 1.5 MV/cm were 3×10−8 A/cm2 and 5×1013 Ω cm, respectively. Typical teff(SiO2) of 1.2 nm was obtained for the a-Ta2O5 film formed on a Ru/TiN/Ti/n+-Si substrate, where a Ru layer can act as an effective barrier against oxidation as well as interdiffusion during annealing. In contrast, the teff(SiO2) of the Ta2O5 film prepared on a conventional TiN/Ti/n+-Si substrate was increased by interfacial degradation. Technology employing Ru bottom electrodes and dry-O3 annealing will open a new era of logic embedded memory for 1 Gbit generation. © 1999 American Institute of Physics.
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73.61.Ng Insulators
73.40.Rw Metal-insulator-metal structures
61.72.Cc Kinetics of defect formation and annealing

On the origin of strong visible photoluminescence in a Ge/porous Si structure

X. L. Wu, G. G. Siu, Y. Gu, N. Tang, T. Gao, and X. M. Bao

Appl. Phys. Lett. 74, 827 (1999); http://dx.doi.org/10.1063/1.123381 (3 pages) | Cited 5 times

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We have studied the origin of strong visible photoluminescence (PL) in a Ge/porous Si (PS) structure in terms of infrared spectroscopy and electron spin resonance (ESR). Spectral analyses indicate that the enhanced PL cannot arise from both the quantum confinement on Ge nanocrystals embedded in the pores and the chemical compound of Ge, O, and H at the surface of the porous Si formed during Ge deposition. The experimental result from ESR strongly suggests that optical transitions in the oxygen-related defect centers (nonbridging oxygen hole centers) at the interface between PS and the Ge layer are responsible for the enhanced PL. © 1999 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
76.30.Lh Other ions and impurities
71.55.Cn Elemental semiconductors

The nature of encapsulated silicon nanoclusters in zeolite Y

J. He, Y. Ba, C. I. Ratcliffe, J. A. Ripmeester, D. D. Klug, and J. S. Tse

Appl. Phys. Lett. 74, 830 (1999); http://dx.doi.org/10.1063/1.123382 (3 pages) | Cited 5 times

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Luminescent silicon clusters have been synthesized by chemical vapor deposition of Si2H6 into the supercages of H32Na24Y zeolite. The encapsulated Si clusters are air stable and exhibit a room-temperature photoluminescence in the green-yellow region. The electronic band gap of the cluster is determined to be about 2.4 eV from photoelectron and photoabsorption spectroscopies. A saturation loading of seven disilane molecules per supercage was determined directly from multiple quantum 1H nuclear magnetic resonance spin counting of the precursor material. Intrazeolitic Sin clusters are formed after heating with loss of SiH4 and H2. The new quantitative spin counting result is consistent with an average value of 12±2 Si/cluster obtained from previous indirect measurements using x-ray photoelectron spectroscopy and Si K-edge x-ray absorption near-edge spectroscopy [J. He, D. D. Klug, J. S. Tse, C. I. Ratcliffe, and K. F. Preston, Appl. Phys. Lett. 71, 3194 (1997)]. This observation reveals a mechanism for the conversion of gaseous Si2H6 into silicon nanoclusters. © 1999 American Institute of Physics.
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78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
71.20.Mq Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
76.60.-k Nuclear magnetic resonance and relaxation
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.70.Dm X-ray absorption spectra

Electron field emission from surface treated tetrahedral amorphous carbon films

X. Shi, L. K. Cheah, B. K. Tay, and S. R. P. Silva

Appl. Phys. Lett. 74, 833 (1999); http://dx.doi.org/10.1063/1.123383 (3 pages) | Cited 21 times

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The electron field emission properties of tetrahedral amorphous carbon thin films deposited using a filtered cathodic vacuum arc system have improved as a result of surface treatment with H, O, and Ar ions. The limiting factor of the emission process does not appear to be only the front surface of the films. The improvement in the emission after ion beam treatment appears to be independent of the ions used. The surface which has been analyzed using ultraviolet photospectroscopy, reflected electron energy loss spectroscopy, and scanning tunneling microscopy shows evidence of the creation of segregated sp2 and sp3 rich regions of less than 20 nm in dimension. An extension to the space charge-induced band bending model including a multistep emission process that occurs in this mixed phase material is proposed. © 1999 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
68.55.-a Thin film structure and morphology
79.60.Dp Adsorbed layers and thin films
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