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1 May 1995

Volume 66, Issue 18, pp. 2309-2438

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Intense blue emission from porous β‐SiC formed on C+‐implanted silicon

Liang‐Sheng Liao, Xi‐Mao Bao, Zhi‐Feng Yang, and Nai‐Ben Min

Appl. Phys. Lett. 66, 2382 (1995); http://dx.doi.org/10.1063/1.113990 (3 pages) | Cited 83 times

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Carbon ions were implanted into crystal silicon wafers at an energy of 50 keV and with a dose of 1017 cm−2 followed by thermal annealing. A layer of polycrystalline β‐SiC was formed beneath the sample surface. Porous nanometer structures were prepared by conventional anodization. At room temperature, the samples exhibit a blue luminescence peak at 2.79 eV (445 nm), which is higher than the energy gap of bulk β‐SiC (2.2 eV), and its intensity is stronger than that of the reference porous silicon. The results could be explained by the quantum confinement effect. © 1995 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Quasi‐one‐dimensional single AlGaAs/GaAs Hall bar quantum wires grown on patterned substrates

T. Shitara, M. Tornow, A. Kurtenbach, D. Weiss, K. Eberl, and K. v. Klitzing

Appl. Phys. Lett. 66, 2385 (1995); http://dx.doi.org/10.1063/1.113991 (3 pages) | Cited 3 times

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Hall bars with widths down to about 250 nm were prepared by overgrowth on patterned GaAs(001) substrates using molecular beam epitaxy. This fabrication method generates a lateral confinement potential determined by AlGaAs barriers. The four‐terminal magnetoresistance of a single wire, measured at 1.3 K after illumination, displays the well‐known features of quasi‐one‐dimensional electron systems. We estimate the electron mobility in a ∼250 nm wide wire to be larger than 51 000 cm2/V s at a carrier concentration of 3.3×1011 cm−2.This mobility is comparable to the one measured in a wide reference sample fabricated under identical conditions. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Modification of excitonic emission in a GaAs bulk microcavity

A. Tredicucci, Y. Chen, V. Pellegrini, and C. Deparis

Appl. Phys. Lett. 66, 2388 (1995); http://dx.doi.org/10.1063/1.113949 (3 pages) | Cited 19 times

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We report the observation of cavity‐induced modifications of the three‐dimensional bulk exciton emission in a planar GaAs microcavity, in which the entire cavity layer is an active material. We have performed standard photoluminescence measurements at various emission angles, obtaining evidence of coupling between the exciton and the cavity mode. The modified density of photon states available for the exciton decay shows up in the angle dependence of the emission lineshape, as well as of the photoluminescence peak intensity. The experimental results are qualitatively clarified with theoretical calculations performed with an adapted transfer‐matrix approach. © 1995 American Institute of Physics.
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71.35.-y Excitons and related phenomena
78.55.Cr III-V semiconductors
42.50.-p Quantum optics

Quantum wirelike induced morphology in InGaAs wells grown on InyAl1−yAs tensile buffer layers over (100)InP vicinal surfaces

F. Peiró, A. Cornet, J. R. Morante, A. Georgakilas, C. Wood, and A. Christou

Appl. Phys. Lett. 66, 2391 (1995); http://dx.doi.org/10.1063/1.113950 (3 pages) | Cited 12 times

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The appearance of quantum wirelike morphology on InGaAs single quantum well structures grown by molecular beam epitaxy on (100)InP vicinal surfaces is reported. The results of transmission electron microscopy reveal that the misorientation of the substrate drives the development of a lateral contrast modulation related to In‐rich or Al‐rich regions oriented along {133} or {122} planes that initiate on the InAlAs tensile buffer layer and propagate across the structure, giving rise to an anisotropic rippling of the InGaAs well. Conversely, a misfit dislocation network at the InAlAs/InP interface was observed for the same layers grown on exact (100) surface. A comparison of the two structures suggest that the development of such modulated configuration is apparently a strain relieving mechanism. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology

Passivation of oxidation induced defects in silicon

A. Correia, D. Ballutaud, and A. Boutry‐Forveille

Appl. Phys. Lett. 66, 2394 (1995); http://dx.doi.org/10.1063/1.113951 (3 pages) | Cited 3 times

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The effects on minority carrier diffusion length and surface recombination velocity of the oxidation of p‐type silicon in a copper contaminated ambient have been analyzed using electron beam induced current. The experiments were carried out on Czochralski and float‐zone silicon in order to obtain two different microstructures of defects and copper precipitation modes at the interface, and to study the influence, respectively, on the diffusion length and surface recombination velocity. The diffusion length was drastically decreased in regions free of extended defects, showing the existence of pointlike recombinant defects in the matrix. In each case, it has been evidenced by electron beam induced current measurements and imaging that these pointlike defects were passivated by hydrogen radio‐frequency plasma annealing, while no effect was observed on extended recombinant defects. © 1995 American Institute of Physics.
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81.65.-b Surface treatments
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Surface dynamics during CdTe growth by molecular beam epitaxy

A. Arnoult and J. Cibert

Appl. Phys. Lett. 66, 2397 (1995); http://dx.doi.org/10.1063/1.113952 (3 pages) | Cited 8 times

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The dynamics of growth of CdTe by molecular beam epitaxy is studied by RHEED intensity oscillations. The transition to growth by step propagation is observed at lower temperature (i.e., the diffusion length is larger) on the Te‐rich (2×1) surface than on the Cd‐rich c(2×2)–(2×1) one. A strong anisotropy is found, which suggests that growth islands are elongated in the [110] direction. In addition, sublimation cannot be neglected, with at least two mechanisms with different activation energies. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Characterization of iron based precipitates in GaAs layers grown by molecular‐beam epitaxy

M. W. Bench, C. B. Carter, Feng Wang, and P. I. Cohen

Appl. Phys. Lett. 66, 2400 (1995); http://dx.doi.org/10.1063/1.113953 (3 pages) | Cited 2 times

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GaAs layers that contain small Fe‐based precipitates have been grown using molecular‐beam epitaxy. The layers were produced either by codepositing Fe during GaAs growth or by first depositing a thin layer of an Fe‐Ga alloy and then growing a capping layer of GaAs. Microstructural characterization of the layers was performed by using transmission electron microscopy. For those samples in which the Fe alloy layer was deposited, the layer disappeared after GaAs growth, leaving behind Fe‐containing precipitates distributed throughout the GaAs overlayer. Precipitates were also formed in Fe codeposited samples. The sizes and number densities of the precipitates were dependent on the growth method used, with mean diameters ranging from 21 to 47 nm and number densities from 1013–1015 per cm3. The phase, orientation, and morphology of the particles were also dependent on the growth conditions used, with FeAs and Fe being observed. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors

GeSi/Si bistable diode exhibiting a large on/off conductance ratio

X. Zheng, T. K. Carns, and K. L. Wang

Appl. Phys. Lett. 66, 2403 (1995); http://dx.doi.org/10.1063/1.113954 (3 pages) | Cited 1 time

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A novel bistable phenomenon having both a high conductance on state and a high impedance off state has been observed in a forward biased delta‐doped GeSi/Si tunnel diode grown by molecular beam epitaxy. The bistable characteristics are attributed to the different mobile carrier densities in the delta‐doped layers, which leads to the switching of the band structure from a tunnel junctionlike alignment to a p‐i‐n junctionlike alignment or vice‐versa. An on/off conductance ratio larger than 106 has been demonstrated for a modified diode structure. The device processing is technologically compatible to the current Si metal‐oxide‐semiconductor technology, making the device useful for a high speed, high density static random access memory cell. © 1995 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)

Substitutionality of Ge atoms in ion implanted AlSb

Kin Man Yu, A. J. Moll, Ning Chan, W. Walukiewicz, and P. Becla

Appl. Phys. Lett. 66, 2406 (1995); http://dx.doi.org/10.1063/1.113955 (3 pages) | Cited 8 times

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The substitution of Ge atoms into ion implanted AlSb is investigated by extended x‐ray absorption fine structure spectroscopy. Our results reveal that in the as‐implanted material, the implanted Ge atoms are equally distributed between two specific sites, one surrounded by Al atoms and the other surrounded by Sb atoms. After annealing at 750 °C for 5 s, the coordination number of the Ge atoms increases from ∼3 to ∼4 indicating solid phase regrowth of the implantation induced amorphous surface layer. Moreover, in the annealed AlSb, the substitution of Ge atoms into the Al sublattice dominates with an estimated GeAl]:[GeSb]∼0.8:0.2. These results suggest that Ge atoms act preferentially as donor species in AlSb. © 1995 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
61.72.J- Point defects and defect clusters

Titanium dioxide photocatalysts produced by reactive magnetron sputtering

B. R. Weinberger and R. B. Garber

Appl. Phys. Lett. 66, 2409 (1995); http://dx.doi.org/10.1063/1.113956 (3 pages) | Cited 38 times

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A process is described for the deposition of anatase titanium dioxide films by reactive magnetron sputtering. The films have a porous columnar morphology with a high effective surface area making them well suited to be used as photocatalysts. Data are presented on the use of such films in the photocatalytic decomposition of gas phase pollutants in air. © 1995 American Institute of Physics.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
81.15.Cd Deposition by sputtering

n‐type doping of the diluted magnetic semiconductor Zn1−xMnxSe

H. Abad, B. T. Jonker, W. Y. Yu, S. Stoltz, and A. Petrou

Appl. Phys. Lett. 66, 2412 (1995); http://dx.doi.org/10.1063/1.113957 (3 pages) | Cited 9 times

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We report on the intentional n‐type doping of the diluted magnetic semiconductor Zn1−xMnxSe using ZnCl2 as the dopant source. Samples with varying Mn concentrations and carrier densities were grown by molecular beam epitaxy and characterized using Hall effect, x‐ray diffraction, and photoluminescence measurements. Net carrier concentrations in excess of 1018 cm−3 are readily obtained for x≤0.08. Useful carrier densities can be achieved for Mn concentrations x≤0.15, above which the samples are highly insulating. The controlled doping of this alloy provides another material for use in the fabrication of wide gap semiconductor device structures. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors

Across wafer etch rate uniformity in a high density plasma reactor: Experiment and modeling

M. Surendra, C. R. Guarnieri, G. S. Selwyn, and M. Dalvie

Appl. Phys. Lett. 66, 2415 (1995); http://dx.doi.org/10.1063/1.113958 (3 pages) | Cited 4 times

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A study of silicon oxide etch rate uniformity in a high density, rf inductively coupled system with an rf capacitively coupled substrate electrode is presented. By introducing spatial variation of rf coupling to the substrate, etch rate uniformity across the wafer can be altered from a profile that is ∼20% higher in the center to one that is ∼10% lower in the center. The effect of spatially varying rf coupling impedance to the substrate is dependent on substrate resistance. Predicted etch rate profiles are obtained with a two‐dimensional analytic model of the plasma source that is coupled to an equivalent circuit discretization of the electrode assembly, substrate, and sheath. Model results compare favorably with experimental measurements. © 1995 American Institute of Physics.
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81.65.-b Surface treatments
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Stoichiometry and thickness variation of YBa2Cu3O7−x in off‐axis pulsed laser deposition

Z. Trajanovic, L. Senapati, R. P. Sharma, and T. Venkatesan

Appl. Phys. Lett. 66, 2418 (1995); http://dx.doi.org/10.1063/1.113959 (3 pages) | Cited 20 times

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We studied the dependence of the thickness and stoichiometry of YBa2Cu3O7−x deposited in an off‐axis pulsed laser deposition geometry on the background oxygen pressure and the distance from the target. We observe a biregional drop‐off in thickness with increasing axial distance, with the border between the two regions at 3–4 cm away from the target. The thickness was proportional to the deposition pressure raised to the 2/3 power, at axial distances greater than 4 cm. Atomic force microscope studies of the two regions showed the density of micron sized particles to be 2–5×104/cm2 within the first region (closer to the target) with no such particles in the second region. The stoichiometric composition did not exhibit this biregional dependence. At an optimum oxygen pressure of 200 mTorr, we were able to obtain a stoichiometrically uniform region as large as 3×4 cm2. © 1995 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
74.78.-w Superconducting films and low-dimensional structures
68.55.Nq Composition and phase identification

Sensitive high‐Tc transition edge bolometer on a micromachined silicon membrane

H. Neff, J. Laukemper, I. A. Khrebtov, A. D. Tkachenko, E. Steinbeiss, W. Michalke, M. Burnus, T. Heidenblut, G. Hefle, and B. Schwierzi

Appl. Phys. Lett. 66, 2421 (1995); http://dx.doi.org/10.1063/1.113960 (3 pages) | Cited 20 times

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Superconducting transition edge bolometers on micromachined silicon membranes have been fabricated. The optical response is 580 V/W at a time constant of 0.4 ms. The detectivity D∗ is 3.8×109 (cm Hz1/2 W−1) at a temperature of 84.5 K and within the frequency regime 100<f<300 Hz. This is one of the fastest composite type bolometers ever reported. Upon thermal optimization, this type of detector should be competitive with state‐of‐the‐art quantum detectors. © 1995 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices

Substrate stress controlled magnetic domains in amorphous Terfenol‐D films

Quanmin Su, Y. Zheng, A. Roytburd, and Manfred Wuttig

Appl. Phys. Lett. 66, 2424 (1995); http://dx.doi.org/10.1063/1.113961 (3 pages) | Cited 6 times

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Magnetic force microscopy of amorphous compressed Terfenol‐D films of micron thickness on both crystalline Si and glassy silica shows that their ferromagnetic domain structure is one dimensional and periodic. On Si the structure is aligned with respect to the easy elastic direction of the substrate. The square of the domain period is proportional to the thickness of the film. All facts indicate that the domain morphology in these films is determined by a substantial elastic contribution to the domain wall and film/substrate interaction energies. © 1995 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Kj Amorphous and quasicrystalline magnetic materials

Perpendicular magnetic anisotropy and strong magneto‐optic properties of SrRuO3 epitaxial films

L. Klein, J. S. Dodge, T. H. Geballe, A. Kapitulnik, A. F. Marshall, L. Antognazza, and K. Char

Appl. Phys. Lett. 66, 2427 (1995); http://dx.doi.org/10.1063/1.113962 (3 pages) | Cited 57 times

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Epitaxial films of the ferromagnetic perovskite SrRuO3 were measured with a bulk magnetometer and with a local magneto‐optic Sagnac interferometer in transmission and in reflection. We find a magnetic easy axis perpendicular to the films, and for saturated remanent magnetization along this direction the Faraday rotation and the Kerr rotation at λ=840 nm are about 0.75×105 deg/cm and 0.85°, respectively. The temperature dependence of the remanent magnetization in the low temperature limit is dominated by spin‐wave excitations, yielding a notable decrease with T3/2. Using Sagnac–Kerr scanning and transmission electron microscopy imaging we correlate the coercivity with the grain size. © 1995 American Institute of Physics.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.30.Gw Magnetic anisotropy
75.50.Dd Nonmetallic ferromagnetic materials

Carbon nanotubes synthesized in a hydrogen arc discharge

X. K. Wang, X. W. Lin, V. P. Dravid, J. B. Ketterson, and R. P. H. Chang

Appl. Phys. Lett. 66, 2430 (1995); http://dx.doi.org/10.1063/1.113963 (3 pages) | Cited 40 times

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We have developed a novel method to synthesize ‘‘clean’’ carbon nanotubes with relatively higher yield using a hydrogen arc discharge. The quality and yield of the tubes depend sensitively on the gas pressure in the arc discharge. We have observed sharp, open‐ended nanotubes with clear lattice fringes at the edges and empty interiors. The existence of these frozen‐open‐ended tubes in the buckybundles provides evidence for an open‐ended growth model for nanotubes. © 1995 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Optical properties of GaN epitaxial films grown by low‐pressure chemical vapor epitaxy using a new nitrogen source: Hydrazoic acid (HN3)

Y. Bu, M. C. Lin, L. P. Fu, D. G. Chtchekine, G. D. Gilliland, Y. Chen, S. E. Ralph, and S. R. Stock

Appl. Phys. Lett. 66, 2433 (1995); http://dx.doi.org/10.1063/1.113964 (3 pages) | Cited 6 times

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We report results of our growth and characterization of GaN films using low‐pressure chemical vapor epitaxy with a new nitrogen source, hydrazoic acid (HN3). This growth technique allows for low‐temperature deposition, low III/V ratios, and increased deposition rates (up to ∼2–3 μm/h). The deposited films show Ga:N atomic ratios of 1±0.25 based on our x‐ray photoelectron spectroscopy analyses, and the He(II) UPS (ultraviolet photoelectron spectroscopy) spectra compare favorably with the semi‐ab initio calculations for the GaN valence bands and with the reported UPS data for single crystal GaN films. X‐ray and Raman spectra show deposited films crystallized in the expected wurtzite structure. We find these epitaxial films to be efficient light emitters in the blue or yellow region of the spectrum, depending upon growth conditions. Our photoluminescence time‐decay kinetics confirm the excitonic nature of the blue emission. Lastly, far infrared time‐domain spectroscopy shows the low carrier concentration of this material. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.47.-p Spectroscopy of solid state dynamics
78.55.Cr III-V semiconductors

Effects of chemical composition on humidity sensitivity of Al/BaTiO3/Si structure

G. Q. Li, P. T. Lai, S. H. Zeng, M. Q. Huang, and B. Y. Liu

Appl. Phys. Lett. 66, 2436 (1995); http://dx.doi.org/10.1063/1.113965 (3 pages) | Cited 9 times

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Argon‐ion‐beam sputtering technique has been applied to deposit barium titanate (BaTiO3) films on silicon wafers at room temperature under vacuum, and then Al/BaTiO3/Si structures were fabricated. Results show that the current and capacitance of these devices are sensitive to the change of relative humidity at room temperature, and saturation absorption (response) time as well as humidity sensitivity of the devices depend on the chemical composition of the BaTiO3 films. For higher annealing temperature and longer annealing time, the oxygen composition increases while fixed charge density decreases. These changes result in lower humidity sensitivity and longer response time. © 1995 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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