By Topic

Applied Physics Letters

Issue 10 • Date Mar 1998

Filter Results

Displaying Results 1 - 25 of 45
  • Issue Cover

    Page(s): c1
    Save to Project icon | PDF file iconPDF (33 KB)  
    Freely Available from IEEE
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (32 KB)  
    Freely Available from IEEE
  • Fabrication of a low-operating voltage diamond thin film metal–semiconductor–metal photodetector by laser writing lithography

    Page(s): 1131 - 1133
    Save to Project icon | PDF file iconPDF (179 KB)  

    An ultraviolet-sensitive photodetector based on the metal-semiconductor-metal structure has been fabricated on a chemical-vapor-deposited diamond thin film grown on a silicon substrate. Device processing techniques employed include maskless laser writing lithography, image reversal processing and sacrificial layer inclusion, which resulted in devices with an electrode finger separation of only 2.5 μm. This allows for a low operating voltage of only 5 V, which is very much lower than what has been achieved so far. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A high-speed free-space traveling wave photodetector

    Page(s): 1134 - 1136
    Save to Project icon | PDF file iconPDF (80 KB)  

    We present and experimentally demonstrate a traveling wave photodetector adapted to the detection of optically carried microwave signals. The synchronous propagation of the detected modulated laser beam with the photogenerated microwave signal is obtained with a diffraction grating. This concept provides a large detection volume which could be suitable for the optical generation of high power/large dynamic range microwave signals. The operating principle of the device is detailed and experimentally demonstrated, over a 0–5 GHz bandwidth, using a coplanar metalsemiconductor-metal waveguide on a GaAs molecular beam epitaxially grown layer. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fiber image guide with subwavelength resolution

    Page(s): 1137 - 1139
    Save to Project icon | PDF file iconPDF (274 KB)  

    A coherent fiber image guide comprised of individual fibers with a core diameter as small as 250 nm is reported. By using optical fibers with a very large difference between the indices of refraction of the core and cladding materials, efficient containment of light inside the core is achieved even for submicron core diameters, without the need for metallization. Images with subwavelength resolution are obtained with such an image guide. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Gain of the mode locked p-Ge laser in the low field region

    Page(s): 1140 - 1142
    Save to Project icon | PDF file iconPDF (63 KB)  

    Following the earlier observation of active mode locking in the high field region of the Voigt configured p-Ge intervalence band laser, presently mode locking in the low field region is also reported. The experimental results on the effective small signal gain for active- as well as for self-mode locked operation are given. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Relationship between the charging damage of test structures and the deposited charge on unpatterned wafers exposed to an electron cyclotron resonance plasma

    Page(s): 1143 - 1145
    Save to Project icon | PDF file iconPDF (144 KB)  

    The correlation between the nonuniformities of plasma parameters (i.e., floating potential) and the induced charging onto the surface of oxide-covered unpatterned 4 in. Si wafers exposed to O2 electron cyclotron resonance (ECR) plasma is investigated. Wafers covered with a 1000 Å oxide layer were exposed to the ECR plasma under nonuniform conditions, and the induced surface charge was mapped on the wafers using contact potential difference technique. Floating potential profiles were monitored using a Langmuir probe. Experimental data indicate that the magnitude of the surface charge is proportional to the deviation of the floating potential from its surface-averaged potential. These results were compared to location of the damage of metal-oxide-semiconductor capacitor test structures exposed to same plasmas. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Measuring the ion current in electrical discharges using radio-frequency current and voltage measurements

    Page(s): 1146 - 1148
    Save to Project icon | PDF file iconPDF (66 KB)  

    This letter describes a technique for measuring the ion current at a semiconductor wafer that is undergoing plasma processing. The technique relies on external measurements of the radio-frequency (rf) current and voltage at the wafer electrode. The rf signals are generated by the rf bias power which is normally applied to wafers during processing. There is no need for any probe inserted into the plasma or for any additional power supplies which might perturb the plasma. To test the technique, comparisons were made with dc measurements of ion current at a bare aluminum electrode, for argon discharges at 1.33 Pa, ion current densities of 1.3–13 mA/cm2, rf bias frequencies of 0.1–10 MHz, and rf bias voltages from 1 to 200 V. Additional tests showed that ion current measurements could be obtained by the rf technique even when electrically insulating wafers were placed on the electrode and when an insulating layer was deposited on the electrode. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Novel microwave plasma reactor for diamond synthesis

    Page(s): 1149 - 1151
    Save to Project icon | PDF file iconPDF (312 KB)  

    Numerical simulations were performed to predict the performance of microwave plasma reactors with various reactor geometries. The simulations include the calculation of the electric field distribution using the finite integration theory and the determination of the plasma density distribution based on a breakdown field algorithm. One reactor geometry with a cavity having the shape of a rotational ellipsoid turned out to be very promising. The electric field within this cavity exhibits two pronounced maxima at the two focal points of the ellipsoid. By coupling microwave energy into one maximum via an antenna, large electric field strengths can be generated in the counter maximum. This effect has been used to excite intense discharges that are very stable, spatially extended, homogeneous, and free from wall contact. These discharges were employed for the chemical vapor deposition of large area diamond wafers. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mechanical parametric amplification in piezoresistive gallium arsenide microcantilevers

    Page(s): 1152 - 1154
    Save to Project icon | PDF file iconPDF (319 KB)  

    Preamplification of mechanical signals in external force detection systems can improve overall sensitivity in a case where sensitivity is limited by secondary detection noise. We report experimental data on degenerate and nondegenerate mechanical parametric amplification in GaAs piezoresistive atomic force microscopy cantilevers due to an inherent mechanical nonlinearity. The mechanical nonlinearity is estimated to be a result of curvature at the cantilever base. Characteristics of parametric amplification such as phase sensitive gain, small signal gain, gain saturation, and self-oscillation have been studied. A small signal phase sensitive gain of 19.5 dB was observed for the degenerate parametric amplifier. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Growing a periodic microstructure on the superconductor crystal surface by electrocrystallization

    Page(s): 1155 - 1157
    Save to Project icon | PDF file iconPDF (284 KB)  

    A novel microstructure is formed on the single crystal surfaces of the oxide superconductor Ba0.6K0.4BiO3 (BKBO). Micron-sized barium islands periodically grew on the mother crystal during electrocrystallization of BKBO. Experimental analysis suggested the relation of this unusual microstructure to the Liesegang rings well-known for a crystal growth in gels. The present discovery provides a potential technology for fabricating microstructures on substrates of solids. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Growth of epitaxial AlxGa1-xN films by pulsed laser deposition

    Page(s): 1158 - 1160
    Save to Project icon | PDF file iconPDF (145 KB)  

    Epitaxial AlxGa1-xN films have been grown on c-cut sapphire substrates at 800 °C and 10-2Torr N2 by pulsed laser deposition (PLD) using a KrF laser. Throughout the composition range from x=0 to 0.6, the films show epitaxial patterns in reflection high-energy electron diffraction, in agreement with the results from x-ray diffraction. The lattice constants of the films vary linearly with x. The composition dependence of the band gaps of the films deviates from linearity and bows downward. This letter reports the application of PLD to controlling the lattice constant and band gap by varying the proportion of AlN and GaN in the target mixture. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Growth and characterization of InNxAsyP1-x-y/InP strained quantum well structures

    Page(s): 1161 - 1163
    Save to Project icon | PDF file iconPDF (85 KB)  

    In this work, we propose the material InNxAsyP1-x-y (InNAsP) on InP for long-wavelength laser applications, where the unique feature of the smaller lattice constant of nitrides together with the large electronegativity of nitrogen atoms has been utilized in reducing the system strain while increasing the conduction-band offset by putting N into a compressively strained material system. InNAsP/In(Ga)(As)P strained quantum well (QW) samples were grown by gas-source molecular beam epitaxy with a rf nitrogen plasma source. Very sharp and distinct satellite peaks as well as Pendellosung fringes are observed in high-resolution x-ray rocking curves for these QWs, indicating good crystalline quality, lateral uniformity, and vertical periodicity. Photoluminescence (PL) measurements on InNAsP/InP single QWs with different well widths as well as on InNAsP/InGaAsP multiple QWs reveal strong PL emissions in the range of from 1.1 to 1.5 μm, demonstrating their suitability for long-wavelength applications. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Formation of silicon nitride layers by nitrogen ion irradiation of silicon biased to a high voltage in an electron cyclotron resonance microwave plasma

    Page(s): 1164 - 1166
    Save to Project icon | PDF file iconPDF (311 KB)  

    Silicon was pulse biased to -50 kV in a nitrogen plasma generated by microwave excitation in electron cyclotron resonance mode. Nitrogen ions from the plasma were accelerated in the electrical field and implanted into the silicon. Cross-section transmission electron microscopy showed that the resulting surface layer was amorphous. Tempering at 1500 K led to the formation of a 25 nm thick continuous crystalline film of α-Si3N4 buried under a 50 nm thick amorphous surface zone. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An in situ Raman study of polarization-dependent photocrystallization in amorphous selenium films

    Page(s): 1167 - 1169
    Save to Project icon | PDF file iconPDF (79 KB)  

    Photocrystallization of amorphous selenium (a-Se) films under illumination by polarized light with 632.8 or 647.1 nm wavelength has been studied by Raman spectroscopy. Preferential orientation of trigonal crystalline, selenium (t-Se) obtained as a result of photocrystallization has been observed, threefold c axis of t-Se being oriented perpendicular to the direction of the polarization of the illuminating light. Although the mechanism of polarization-dependent photocrystallization seems to be optical in origin, an alternative, essentially thermal, mechanism of the polarization-dependent photocrystallization of a-Se is discussed. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Boundary condition effects on field-induced deformation modes in polymer dispersed liquid crystals

    Page(s): 1170 - 1172
    Save to Project icon | PDF file iconPDF (120 KB)  

    Electric field-induced deformation modes, which are considered one of the causes of the hysteresis in the V-T response of polymer dispersed liquid crystal (PDLC), were investigated. We constructed model PDLC cells with varied alignment treatments at the interface of the liquid crystal droplets. The electric field-induced deformation modes of the liquid crystals in the model cells were analyzed by polarized microscope observations. Our results suggested a possible way to hysteresis-free PDLC devices. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Self-organized formation of hexagonal pore arrays in anodic alumina

    Page(s): 1173 - 1175
    Save to Project icon | PDF file iconPDF (309 KB)  

    The conditions for the self-organized formation of ordered hexagonal structures in anodic alumina were investigated for both oxalic and sulfuric acid as an electrolyte. Highly ordered pore arrays were obtained for oxidation in both acids. The size of the ordered domains depends strongly on the anodizing voltage. This effect is correlated with a voltage dependence of the volume expansion of the aluminum during oxidation and the current efficiency for oxide formation. The resulting mechanical stress at the metal/oxide interface is proposed to cause repulsive forces between the neighboring pores which promote the formation of ordered hexagonal pore arrays. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Favorable formation of the C49-TiSi2 phase on Si(001) determined by first-principles calculations

    Page(s): 1176 - 1178
    Save to Project icon | PDF file iconPDF (88 KB)  

    Using first-principles total-energy calculations, we investigated the atomic structure of a very thin Ti film on Si(001) and their intermixing. Our calculations show that the Ti film forms a pseudomorphic body-centered-tetragonal structure on Si(001). We found that intermixing of Ti and Si atoms energetically favors the formation of a C49-TiSi2 phase. We propose a plausible explanation of how the C49-TiSi2 phase and the interfacial structure between C49 phase and Si(001) are formed. We discuss why the transformation of the C49 phase into the C54 phase is inhibited when the TiSi2 dimensions reach the submicron region. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • c-axis oriented ferroelectric thin films of Si-substituted PbTiO3 on Si(100) by pulsed laser deposition: Boost for nonvolatile memory application

    Page(s): 1179 - 1181
    Save to Project icon | PDF file iconPDF (58 KB)  

    It has been demonstrated that Si substitution in a PbTiO3 target helps to avoid the formation of a pyrochlore phase, which otherwise occurs during fabrication of the films directly on Si(100) by the pulsed laser deposition technique. The films are perfectly c-axis oriented. Moreover, the ferroelectric properties of PbTiO3 are not affected by Si substitution. As silicon helps the realization of the films at low substrate temperature, the Pb/Ti ratio is maintained close to 1 and the loss factor tan δ in the range of 0.02–0.05. Thus, the integration of nonvolatile ferroelectric random access memory on semiconductors is shown to be possible in a reliable, cost effective, and simple manner. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Improvement of (Pb1-xLax)(ZryTi1-y)1-x/4O3 ferroelectric thin films by use of SrRuO3/Ru/Pt/Ti bottom electrodes

    Page(s): 1182 - 1184
    Save to Project icon | PDF file iconPDF (87 KB)  

    This work deposits (Pb1-xLax)(ZryTi1-y)1-x/4O3 (PLZT) thin films, possessing good ferroelectric properties (Pr=14.4 μC/cm2), on Pt/Ti/SiO2/Si substrates, using SrRuO3 perovskite as bottom electrodes. Precoating a metallic Ru layer on Pt/Ti/SiO2/Si substrates prior to depositing SrRuO3 bottom electrode further improves the film electrical properties. The optimum ferroelectric properties achieved are Pr=25.6 μC/cm2, Ec=47.1 kV/cm, and Єr=1204. Analyzing the elemental depth profiles using secondary ions mass spectroscopy reveals that the presence of the metallic Ru layer effectively suppresses the outward diffusion of Ti and Si species. The interdiffusion between the SrRuO3 layer and the subsequently deposited PLZT is also substantially reduced, an effect that is presumed to be the primary factor in improving ferroelectric properties for PLZT thin films. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • SrBi2Ta2O9 memory capacitor on Si with a silicon nitride buffer

    Page(s): 1185 - 1186
    Save to Project icon | PDF file iconPDF (72 KB)  

    We have made ferroelectric memory capacitors by depositing a SrBi2Ta2O9 thin film on a Si substrate separated by an ultrathin buffer layer of silicon nitride film. The hysteresis in the capacitance–voltage curves suggests a sizable memory window of 2 V with a programming voltage swing of ±7 V. The switching time is estimated to be on the order of nanosecond based on the results of a one-shot pulse experiment. The results from the fatigue test indicate a slight degradation of the memory window after 1011 switching cycles. These properties are encouraging for the development of ferroelectric memory transistors. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Chemical vapor deposition of ultrathin Ta2O5 films using Ta[N(CH3)2]5

    Page(s): 1187 - 1189
    Save to Project icon | PDF file iconPDF (88 KB)  

    Tantalum oxide films were deposited on Si substrates by chemical vapor deposition using the precursor Ta[N(CH3)2]5, and an oxidizing agent—O2, H2O, or NO. Temperatures ranged between 400 and 500 °C and total pressures between 10-3 and 9 Torr. NO did not lead to satisfactory film growth rates. Insignificant (≪1 at. %) N and up to a few percent C are incorporated when O2 is the oxidant and the total pressure is in the Torr regime. In the milliTorr regime, the Ta2O5 films, grown using either O2 or H2O, contain readily detectable amounts of C and N. For the films grown with O2 in the Torr regime, leakage currents were significantly lowered when the flow rate of O2 increased from 100 to 900 sccm. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Annealing of ion implanted gallium nitride

    Page(s): 1190 - 1192
    Save to Project icon | PDF file iconPDF (138 KB)  

    In this paper, we examine Si and Te ion implant damage removal in GaN as a function of implantation dose, and implantation and annealing temperature. Transmission electron microscopy shows that amorphous layers, which can result from high-dose implantation, recrystallize between 800 and 1100 °C to very defective polycrystalline material. Lower-dose implants (down to 5×1013cm-2), which are not amorphous but defective after implantation, also anneal poorly up to 1100 °C, leaving a coarse network of extended defects. Despite such disorder, a high fraction of Te is found to be substitutional in GaN both following implantation and after annealing. Furthermore, although elevated-temperature implants result in less disorder after implantation, this damage is also impossible to anneal out completely by 1100 °C. The implications of this study are that considerably higher annealing temperatures will be needed to remove damage for optimum electrical properties. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modulation doping of InAs/AlSb quantum wells using remote InAs donor layers

    Page(s): 1193 - 1195
    Save to Project icon | PDF file iconPDF (69 KB)  

    Sheet carrier concentrations in quantum wells of InAs clad by AlSb were enhanced by modulation doping with very thin (9–12 Å) remote InAs(Si) donor layers. The growth temperature of the donor layers was a key parameter, with relatively low temperatures required to minimize Si segregation into the AlSb. Sheet carrier concentrations as high as 3.2×1012/cm2 and 5.6×1012/cm2 were achieved by single- and double-sided modulation doping, respectively. High electron mobility transistors fabricated using the modulation doped structure exhibited a unity current gain cut-off frequency of 60 GHz for a 0.5 μm gate length at a source-drain voltage of 0.5 V. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spatial resolution of capacitance-voltage profiles in quantum well structures

    Page(s): 1196 - 1198
    Save to Project icon | PDF file iconPDF (63 KB)  

    The temperature dependence of the spatial resolution of capacitance-voltage (C-V) profiles in the compositional quantum well (CQW) is investigated. The apparent carrier distribution (ACD) peak in the In0.2Ga0.8As/GaAs single QW is observed to show a strong temperature dependence, compared to that in Si δ-doped GaAs. The ACD peak in CQW is wider (narrower) than the spatial extent of ground-state wave function at high (low) temperatures. The self-consistent numerical simulations on the carrier distribution show that the full width at half maximum of ACD peak in CQW is mainly affected by the debye averaging process at high temperatures and the change in the position expectation value of the two-dimensional electrons at low temperatures. This change in the position expectation value is found to be much smaller than the spatial extent of ground-state electron wave function. © 1998 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

Applied Physics Letters, published by the American Institute of Physics, features concise, up-to-date reports on significant new findings in applied physics.

Full Aims & Scope

Meet Our Editors

Editor
Nghi Q. Lam
Argonne National Laboratory