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17 Jan 1994

Volume 64, Issue 3, pp. 261-393

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Intensity dependence of photoluminescence in GaN thin films

R. Singh, R. J. Molnar, M. S. Ünlü, and T. D. Moustakas

Appl. Phys. Lett. 64, 336 (1994); http://dx.doi.org/10.1063/1.111968 (3 pages) | Cited 64 times

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We report the intensity dependence of band‐gap and midgap photoluminescence in GaN films grown by electron cyclotron resonance (ECR) microwave plasma‐assisted molecular beam epitaxy. We find that the band‐gap luminescence depends linearly while the midgap luminescence has a nonlinear dependence on the incident light intensity. These data were compared with a simple recombination model which assumes a density of recombination centers 2.2 eV below the conduction band edge. The concentration of these centers is higher in films grown at higher microwave power in the ECR plasma.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

High quality aluminum nitride epitaxial layers grown on sapphire substrates

A. Saxler, P. Kung, C. J. Sun, E. Bigan, and M. Razeghi

Appl. Phys. Lett. 64, 339 (1994); http://dx.doi.org/10.1063/1.111168 (3 pages) | Cited 57 times

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In this letter we report the growth of high quality AlN epitaxial layers on sapphire substrates. The AlN grown on (00⋅1) sapphire exhibited a better crystalline quality than that grown on (01⋅2) sapphire. An x‐ray rocking curve of AlN on (00⋅1) Al2O3 yielded a full width at half‐maximum of 97.2 arcsec, which is the narrowest value reported to our knowledge. The AlN peak on (01⋅2) Al2O3 was about 30 times wider. The absorption edge measured by ultraviolet transmission spectroscopy for AlN grown on (00⋅1) Al2O3 was about 197 nm.
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68.55.-a Thin film structure and morphology
78.40.Ha Other nonmetallic inorganics
78.66.Fd III-V semiconductors

Delineation of semiconductor doping by scanning resistance microscopy

C. Shafai, D. J. Thomson, M. Simard‐Normandin, G. Mattiussi, and P. J. Scanlon

Appl. Phys. Lett. 64, 342 (1994); http://dx.doi.org/10.1063/1.111169 (3 pages) | Cited 42 times

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A new technique for the two‐dimensional delineation of P‐N junctions is presented using a scanning resistance microscope (SRM). The SRM uses a conducting probe to perform localized resistance measurements over a surface. These measurements are used to delineate between regions of different doping type and concentration. By using contact forces of 10−4 N, the contact area is estimated to be 30 nm. Experiments have shown the SRM capable of junction delineation with a lateral spacial resolution of less than 35 nm. In addition, during resistance measurements the SRM performs simultaneous surface topography measurements.  
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.30.De Semiconductor-device characterization, design, and modeling

Simultaneous shallow‐junction formation and gate doping p‐channel metal‐semiconductor‐oxide field‐effect transistor process using cobalt silicide as a diffusion/doping source

Wei‐Ming Chen, Jengping Lin, Sanjay K. Banerjee, and Jack C. Lee

Appl. Phys. Lett. 64, 345 (1994); http://dx.doi.org/10.1063/1.111143 (3 pages) | Cited 4 times

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Submicron p‐metal‐semiconductor‐oxide field‐effect transistors (MOSFETs) have been fabricated using cobalt silicide as a diffusion source for forming shallow p‐n junctions and as a doping source for undoped as‐deposited amorphous silicon gate (SADDS). The thermal stability of CoSi2 on polycrystalline silicon is shown to be significantly improved by using as‐deposited amorphous silicon instead of as‐deposited polycrystalline silicon as the gate material. The p‐MOSFETs fabricated using the SADDS process exhibit excellent characteristics and open up the possibility of eliminating several masks and implants in more complicated complimentary metal‐oxide semiconductor processes.  
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85.30.Tv Field effect devices
85.40.Hp Lithography, masks and pattern transfer
61.72.uf Ge and Si
66.30.J- Diffusion of impurities

Logarithmically graded quantum well far‐infrared modulator

P. F. Hopkins, K. L. Campman, G. Bellomi, A. C. Gossard, M. Sundaram, E. L. Yuh, and E. G. Gwinn

Appl. Phys. Lett. 64, 348 (1994); http://dx.doi.org/10.1063/1.111144 (3 pages) | Cited 8 times

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We have designed and fabricated a remotely doped ‘‘logarithmic’’ potential well intended to have a tunable, narrow band absorption at far‐infrared frequencies. A surface gate, epitaxially grown backgate, and contact to the electron gas in the quantum well allow independent control of the absorption frequency and the integrated absorption strength. The resonance frequency is dominated by the well curvature at the potential minimum and can be Stark shifted from ω/2πc=35 cm−1 to a frequency of 125 cm−1 by moving the electron gas through the asymmetric well.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
42.79.Hp Optical processors, correlators, and modulators
78.30.Fs III-V and II-VI semiconductors

Lattice location and electrical activity of Ge co‐implanted with P into InP

Per Kringhøj

Appl. Phys. Lett. 64, 351 (1994); http://dx.doi.org/10.1063/1.111145 (3 pages) | Cited 11 times

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The lattice location and electrical activation of Ge co‐implanted with P or Se has been monitored by employing Rutherford backscattering spectrometry combined with proton‐induced x‐ray emission and differential Hall/resistivity measurements. The substitutional lattice location of Ge co‐implanted with P is the In site, in contrast to a Ge‐only implant where the Ge atoms occupy both lattice sites equally. Both P and Se co‐implantation result in a significantly higher electrical activation, in agreement with the strongly reduced amphoteric behavior of Ge seen in channeling.
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61.72.uj III-V and II-VI semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
71.55.Eq III-V semiconductors

Carrier distribution in silicon devices by atomic force microscopy on etched surfaces

V. Raineri, V. Privitera, W. Vandervorst, L. Hellemans, and J. Snauwaert

Appl. Phys. Lett. 64, 354 (1994); http://dx.doi.org/10.1063/1.111146 (3 pages) | Cited 13 times

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The selective chemical etching of silicon containing an impurity profile was used to obtain surface topography related to the local carrier concentration. Atomic force microscopy (AFM) was then used to image this topography. Through a calibration curve of etched depth versus carrier concentration, established by etching uniformly doped epitaxial silicon layers, it is possible to convert the AFM topographical data into carrier concentration. The technique was applied to measure directly the carrier distribution in submicron devices.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling

Effective mass and quantum lifetime in a Si/Si0.87Ge0.13/Si two‐dimensional hole gas

T. E. Whall, N. L. Mattey, A. D. Plews, P. J. Phillips, O. A. Mironov, R. J. Nicholas, and M. J. Kearney

Appl. Phys. Lett. 64, 357 (1994); http://dx.doi.org/10.1063/1.111147 (3 pages) | Cited 22 times

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Measurements of Shubnikov de Haas oscillations in the temperature range 0.3–2 K have been used to determine an effective mass of 0.23 m0 in a Si/Si0.87Ge0.13/Si two‐dimensional hole gas. This value is in agreement with theoretical predictions and with that obtained from cyclotron resonance measurements. The ratio of the transport time to the quantum lifetime is found to be 0.8. It is concluded that the 4 K hole mobility of 11 000 cm2 V−1 s−1 at a carrier sheet density of 2.2×1011 cm−2 is limited by interface roughness and short‐range interface charge scattering.
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71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Boron‐controlled solid phase epitaxy of germanium on silicon: A new nonsegregating surfactant

J. Klatt, D. Krüger, E. Bugiel, and H. J. Osten

Appl. Phys. Lett. 64, 360 (1994); http://dx.doi.org/10.1063/1.111148 (3 pages) | Cited 3 times

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10‐nm‐thick germanium layers have been grown on Si(100) with boron as a surfactant with three different growth procedures, and investigated with reflection high‐energy electron diffraction, transmission electron microscopy, and secondary ion mass spectroscopy. We obtained smooth and completely closed epitaxial germanium layers only by depositing the boron on top of the amorphous germanium layer followed by a post‐annealing step. The surface energy anisotropy of the germanium will be affected by the presence of boron in this equilibrium process. The islanding observed in all other growth processes can be understood by taking into account that boron is a typical nonsegregating material in Ge below 600 °C and a surfactant acts mainly due to its presence in the growing front.
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81.15.Np Solid phase epitaxy; growth from solid phases

Formation of GaAs ridge quantum wire structures by molecular beam epitaxy on patterned substrates

S. Koshiba, H. Noge, H. Akiyama, T. Inoshita, Y. Nakamura, A. Shimizu, Y. Nagamune, M. Tsuchiya, H. Kano, H. Sakaki, and K. Wada

Appl. Phys. Lett. 64, 363 (1994); http://dx.doi.org/10.1063/1.111967 (3 pages) | Cited 61 times

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A ridge quantum wire structure has been successfully fabricated on a patterned (001) GaAs substrate by first growing a (111)B facet structure with a very sharp ridge and then depositing a thin GaAs quantum well on its top. Electron microscope study has shown that a GaAs wire with the effective lateral width of 17–18 nm is formed at the ridge top. Photoluminescence and cathodoluminescence measurements indicate that one of the luminescence lines comes from the wire region at the ridge and its blue shift (∼60 meV) agrees with the quantum confined energy calculated for the observed wire structure.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Low‐noise YBa2Cu3O7 ‐PrBa2Cu3O7 multiturn flux transformers

M. N. Keene, S. W. Goodyear, N. G. Chew, R. G. Humphreys, J. S. Satchell, J. A. Edwards, and K. Lander

Appl. Phys. Lett. 64, 366 (1994); http://dx.doi.org/10.1063/1.111149 (3 pages) | Cited 14 times

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Epitaxial thin‐film YBa2Cu3O7 flux transformers with multiturn input coils have been constructed on 1 cm2 MgO substrates using PrBa2Cu3O7 as an insulator. By coupling these to high‐temperature superconducting quantum interference devices (SQUIDs) using a flip‐chip technology, several low‐noise magnetometers and a gradiometer have been constructed. The yield of fully working flux transformers on 1 cm2 substrates exceeds 80%, and field sensitivities at 77 K of (520±30)fT/√Hz at 1 Hz and (165±8)fT/√Hz above 10 Hz have been achieved. No evidence for excess low‐frequency noise above that of the uncoupled SQUID has been found in the flip‐chip magnetometers.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.78.-w Superconducting films and low-dimensional structures

As‐grown superconducting Bi2Si2Ca2Cu3Ox thin films with Tczero of 102 K prepared by rf magnetron sputtering

Kazushige Ohbayashi, Takehiko Ohtsuki, Hiroshi Matsushita, Hideaki Nishiwaki, Yoshiaki Takai, and Hisao Hayakawa

Appl. Phys. Lett. 64, 369 (1994); http://dx.doi.org/10.1063/1.111150 (3 pages) | Cited 13 times

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As‐grown high‐quality superconducting thin films of the Bi2Sr2Ca2Cu3Ox were prepared by rf magnetron sputtering with a regulated shuttering technique. 2223 phase films with a 2201 phase buffer layer were deposited on MgO(100) substrates under rigorous control of the film composition, especially of bismuth contents. As a source of bismuth a sufficiently presputtered Bi2O3 target was used. At the preparation, Bi‐Sr‐Cu‐O and Ca‐Cu‐O blocks were deposited alternately, no post‐treatment steps were performed. The zero resistivity critical temperature of the as‐grown film was 102.5 K and the critical current density at 4.2 K was 1.5×107 A/cm2. The growth rate was about 360 Å/h.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
81.15.Cd Deposition by sputtering
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Block‐by‐block deposition: A new growth method for complex oxide thin films

Jean‐Pierre Locquet, André Catana, Erich Mächler, Christoph Gerber, and J. Georg Bednorz

Appl. Phys. Lett. 64, 372 (1994); http://dx.doi.org/10.1063/1.111151 (3 pages) | Cited 50 times

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An alternative growth method for high‐Tc oxide thin films employing molecular beam deposition is proposed. Instead of an uncontrolled local nucleation followed by lateral growth and island coalescence, the new method provides substrate coverage by nonreacting constituents before nucleation is initiated, a controlled reaction path, and reduced lateral growth. DyBa2Cu3O6+δ films without precipitates, with a surface roughness of ±1 unit cell and showing finite size oscillations in the x‐ray diffraction spectrum, have been prepared. This method reveals that diffusion dominates the growth process at high substrate temperatures (≂700 °C).
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74.78.-w Superconducting films and low-dimensional structures
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology

Structural characterization and microwave loss of Nd1.85Ce0.15CuO4−y superconducting thin films on yttria‐stabilized zirconia buffered sapphire

S. N. Mao, X. X. Xi, Jian Mao, D. H. Wu, Qi Li, S. M. Anlage, T. Venkatesan, D. Prasad Beesabathina, L. Salamanca‐Riba, and X. D. Wu

Appl. Phys. Lett. 64, 375 (1994); http://dx.doi.org/10.1063/1.111152 (3 pages) | Cited 7 times

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We have grown superconducting Nd1.85Ce0.15CuO4−y (NCCO) thin films on (1102) sapphire using a yttria‐stabilized zirconia (YSZ) buffer layer, which has been demonstrated to be the best material for the growth of n‐type superconducting NCCO thin films. The films are c‐axis oriented, epitaxially grown with a small mosaic spread of 0.2° and a Rutherford backscattering spectroscopy channeling yield of ∼9%. Cross‐sectional transmission electron microscopy images reveal a sharp interface between NCCO and YSZ. The microwave surface resistance of NCCO films on YSZ buffered sapphire at 9.6 GHz is only 80 μΩ at 4.2 K in zero magnetic field, which is comparable to Y1Ba2Cu3O7−y films at similar reduced temperature, as a consequence of the decrease of structural imperfection in the film. The temperature dependence of the surface resistance and magnetic penetration depth in these films further confirms the s‐wave BCS nature of NCCO.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.N- Response to electromagnetic fields
68.55.-a Thin film structure and morphology

Oxygen control of dc‐sputtered Bi2Sr2Ca1Cu2O8+δ films

Jürgen Auge, Ulrich Rüdiger, Hartmut Frank, Hartmut G. Roskos, Gernot Güntherodt, and Heinrich Kurz

Appl. Phys. Lett. 64, 378 (1994); http://dx.doi.org/10.1063/1.111153 (3 pages) | Cited 11 times

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We report the preparation of Tc‐optimized Bi2Sr2Ca1Cu2O8+δ thin films on SrTiO3 substrates using a planar dc‐sputtering method. The oxygen content of these films is adjusted in situ by controlling the oxygen flow during sputtering. The oxygen content can be varied continuously from the overdoped state (Tc=72 K) to the condition with optimum oxygen content (Tc=88 K), and further, to the underdoped state (Tc=76 K). The oxygen content is determined by x‐ray measurements of the c‐axis lattice parameter.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
81.15.Cd Deposition by sputtering
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Magnetic structure determination for Fe3O4/NiO superlattices

J. A. Borchers, R. W. Erwin, S. D. Berry, D. M. Lind, E. Lochner, and K. A. Shaw

Appl. Phys. Lett. 64, 381 (1994); http://dx.doi.org/10.1063/1.111154 (3 pages) | Cited 11 times

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Neutron diffraction measurements reveal the nature of the magnetic structure in Fe3O4/NiO superlattices grown by molecular beam epitaxy. Taking advantage of differences between the Fe3O4 and NiO crystalline symmetries, we have determined independently the magnetic order parameters of the bilayer components. The NiO antiferromagnetic order propagates coherently through several superlattice bilayers, while the magnetic coherence of the ferrimagnetic Fe3O4 is restricted to a single interlayer due to the random stacking of the spinel unit cells at the interfaces. A model for the diffraction data, based upon a Hendricks–Teller description of the interfacial disorder, demonstrates that the observed broadening of selected reflections originates directly from these stacking faults.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Radio frequency reactive sputtered iron nitrides using ammonia gas: Structure and magnetic properties

John Q. Xiao and C. L. Chien

Appl. Phys. Lett. 64, 384 (1994); http://dx.doi.org/10.1063/1.111155 (3 pages) | Cited 24 times

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Iron nitrides of γ′‐Fe4N, ϵ‐Fe2‐3N, and ζ‐Fe2N have been fabricated using rf sputtering with reactive NH3 gas, which offers significant advantages over the conventional N2 gas. All but ζ‐Fe2N nitride films have relative high saturation moments with a large in‐plane anisotropy. The Mössbauer results are consistent with structural analyses and those from bulk samples.
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75.50.Dd Nonmetallic ferromagnetic materials
75.60.-d Domain effects, magnetization curves, and hysteresis
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

Laser‐assisted thermochemical processing of diamond

Hajime Miyazawa, Shojiro Miyake, Syuichi Watanabe, Masao Murakawa, and Toshiyuki Miyazaki

Appl. Phys. Lett. 64, 387 (1994); http://dx.doi.org/10.1063/1.111156 (3 pages) | Cited 3 times

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A new technique of contamination‐free thermochemical processing of diamond is proposed. A diamond plate, which is placed on a metal plate, is treated thermochemically from its lower surface, in liquid, using a laser as the heat source. A focused Q‐switched YAG laser beam was introduced, which passed through the liquid and diamond, onto the metal plate. The laser beam heats up the metal, and thereby, the lower surface of the diamond is etched by thermochemical interaction with the liquid. Comparison of the liquids, de‐ionized water, and KOH solution, proved that KOH solution is preferable to water with respect to the stability of machining and smoothness of the prepared surface.
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81.65.-b Surface treatments
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

Low voltage electron beam lithography in self‐assembled ultrathin films with the scanning tunneling microscope

C. R. K. Marrian, F. K. Perkins, S. L. Brandow, T. S. Koloski, E. A. Dobisz, and J. M. Calvert

Appl. Phys. Lett. 64, 390 (1994); http://dx.doi.org/10.1063/1.111157 (3 pages) | Cited 46 times

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With a scanning tunneling microscope (STM) operating in vacuum, we have studied the lithographic patterning of self‐assembling organosilane monolayer resist films. Where the organic group is benzyl chloride, the resist layer can be patterned with electrons down to 4 eV in energy. The patterned films have been used as templates for the electroless plating of thin Ni films. Linewidths down to ∼20 nm have been observed in scanning electron micrographs of the plated films. Still smaller features are observed in STM images of the exposed organosilane films.
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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
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
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Comment on ‘‘Source of sidelobe asymmetry in integrated acousto‐optic filters’’ [Appl. Phys. Lett. 62, 814 (1993)]

W. R. Trutna and David W. Dolfi

Appl. Phys. Lett. 64, 393 (1994); http://dx.doi.org/10.1063/1.111158 (1 page) | Cited 1 time

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Abstract Unavailable
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78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
42.79.Ci Filters, zone plates, and polarizers
42.25.Lc Birefringence
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