By Topic

Applied Physics Letters

Issue 13 • Date Mar 1988

Filter Results

Displaying Results 1 - 25 of 26
  • Poled electro‐optic waveguide formation in thin‐film organic media

    Page(s): 1031 - 1033
    Save to Project icon | PDF file iconPDF (591 KB)  

    We describe a novel technique for the fabrication of electro‐optic (EO) waveguides in integrated optic device structures employing organic EO materials. The technique combines the poling and waveguide formation steps by utilizing patterned poling electrodes and the induced birefringence associated with the poling process. Several prototype waveguide devices fabricated using this procedure are reported. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Row‐backlight, column‐shutter display concept

    Page(s): 1034 - 1036
    Save to Project icon | PDF file iconPDF (541 KB)  

    Feasibility of a novel flat‐panel liquid‐crystal display that is capable of full‐motion video but does not require active elements at each pixel is shown. It can use the wide viewing angle, high contrast, and high speed of ferroelectric liquid crystals while being insensitive to their lack of a definite field threshold. To demonstrate this display, a linear array of ferroelectric liquid‐crystal shutters is driven to permit or block the view of rows that are illuminated one after another on an oscilloscope. At 15 V drive the shutters respond in 100 μs, which would be within the time available per row if the top and bottom halves of a display were to be addressed separately. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient, high‐power (≫150 mW) grating surface emitting lasers

    Page(s): 1037 - 1039
    Save to Project icon | PDF file iconPDF (589 KB)  

    Surface emitting AlGaAs second‐order distributed Bragg reflector lasers using a superlattice graded‐index separate confinement heterostructure with a single quantum well have been fabricated. The total peak power is emitted coherently from both gratings into a 0.06° full width half‐power single lobe far field pattern. Peak powers are in excess of 150 mW. The external differential quantum efficiency is as high as 30%. Under severe current modulation conditions, the stable single longitudinal mode had 20–45 dB wavelength side mode rejection. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Laser action in chromium‐doped forsterite

    Page(s): 1040 - 1042
    Save to Project icon | PDF file iconPDF (555 KB)  

    Room‐temperature vibronic pulsed laser action in trivalent chromium‐activated forsterite (Cr3+:Mg2SiO4) is reported for the first time. The free‐running laser emission is centered at 1235 nm of the broad 4T24A2 fluorescence band, and has a bandwidth of ∼22 nm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Twin formation and Au segregation during ion‐beam‐induced epitaxy of amorphous Si

    Page(s): 1043 - 1045
    Save to Project icon | PDF file iconPDF (695 KB)  

    Ion‐beam‐induced epitaxial recrystallization of Au‐implanted amorphous silicon at temperatures ≫400 °C has been studied. Crystallization was induced using a 2.5 MeV Ar beam. Segregation of Au at the moving crystal/amorphous silicon interface occurs with an interface velocity of 5 Å/s. At high Au concentrations, the interface breaks down with the formation of twins. The twinned crystal/amorphous interface then propagates under further irradiation with a reduced interface velocity of 3 Å/s. Unusual Au redistribution profiles are obtained as a result of the sudden change in interface morphology. The Au profiles are interpreted on the basis of classical segregation theory with the interfacial segregation coefficient changing from 0.0012 to 0.02 at the onset of twin formation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wear reduction of glassy carbon by Li implantation

    Page(s): 1046 - 1047
    Save to Project icon | PDF file iconPDF (392 KB)  

    A study has been made of the effect of Li implantation on wear properties of glassy carbon (GC). Abrasive wear tests with a silicon carbide abrasive paper showed that Li implantation greatly reduced the wear volume of GC. Raman spectroscopy indicated that Li implantation changes the surface structure from disordered graphite to amorphous. Depth profiles of Li measured by secondary ion mass spectroscopy showed the migration of Li atoms towards the surface. It is concluded that the reduction of wear volume due to Li implantation may be caused by the formation of amorphous structure and/or the surface enrichment of implanted Li atoms. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time‐resolved measurement of space charge in polymeric material under prebreakdown ac field

    Page(s): 1048 - 1049
    Save to Project icon | PDF file iconPDF (424 KB)  

    The buildup of space charge following carrier injection under a prebreakdown field is often considered as a possible degradation process of a polymeric material. The energy released during trapping (phonons and photons) might be at the origin of bond breaking, even if the details of this process are not completely elucidated. Space‐charge formation is of particular importance during ac stressing, since the nature of the trapped charge depends on stress polarity. We present in the following a very sensitive and new experimental setup that allows for the first time the analog, time‐resolved measurement of trapped charge during ac polarization at high field in a dielectric material. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ellipsometric spectra of silicon‐on‐insulator wafers

    Page(s): 1050 - 1052
    Save to Project icon | PDF file iconPDF (520 KB)  

    Spectroellipsometry (SE) has been used to investigate the silicon‐on‐insulator (SOI) structures formed by oxygen ion implanted into silicon and the corresponding annealed samples. A simple equation to estimate the thickness of the SOI structure is presented. Using a multilayer model and the Bruggeman effective medium approximation, we have analyzed the thicknesses and compositions of the SOI structures. Having been compared with the results determined by the Rutherford backscattering, spreading resistance probe, and infrared absorption measurements, our results show that, after high‐temperature annealing, the top layer of the SOI structure is close to a perfect single crystal silicon, and the buried SiO2 is in a disorder phase. The thicknesses determined by all these measurements are in good agreement with each other. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Low‐temperature epitaxial growth of silicon by low‐pressure chemical vapor deposition

    Page(s): 1053 - 1055
    Save to Project icon | PDF file iconPDF (685 KB)  

    Low‐pressure chemical deposition of silicon by the pyrolysis of pure silane at relatively low temperatures and pressures below 100 mTorr can lead to structurally well‐defined films. Below 10 mTorr the films exhibit evidence of local epitaxial growth, which can be particularly well defined on Si(100) wafers chemically treated prior to deposition outside the deposition chamber. Even so, the interface was found to be highly strained, and high‐resolution electron microscopy observations were used to analyze the defect structures in the epitaxial layer as initiated at the interface. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electron beam oxidation of semiconductors (one mechanism of electron beam processes)

    Page(s): 1056 - 1058
    Save to Project icon | PDF file iconPDF (535 KB)  

    New types of oxide layers of Si and GaAs were grown on (100) Si and (100) GaAs substrate by using an electron beam doping technique at 40–50 °C. The surfaces of the semiconductors were irradiated with a fluence of ∼5×1017 electrons cm-2 at 7 MeV. The samples were put in an isothermal circulating water bath with a thermoregulator. The electronic structure of the oxide layers was observed by an x‐ray photoelectron spectroscopy (XPS). The chemical shifts between oxidized and nonoxidized Ga signals for Auger electron spectra and 3d XPS spectra were nearly equal to that in the conventional plasma‐grown oxidation. It was suggested that the electron beam doping, oxidation, and epitaxy were caused by plasma reaction. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • X‐ray study of the crystalline structure of CdTe layers grown on (001), (111)A, and (111)B CdTe surfaces by metalorganic chemical vapor deposition

    Page(s): 1059 - 1061
    Save to Project icon | PDF file iconPDF (587 KB)  

    CdTe layers grown by metalorganic chemical vapor deposition on (111)A, (111)B, and (001) CdTe substrates exhibited substantial differences in crystalline microstructure. Double crystal diffractometry was used to resolve and identify the (111) microtwins. (111)B layers were found to be composed of lamella microtwins, while (111)A layers contained double positioning type twins and had a better structural quality. (001) layers exhibited the best crystalline quality and were found to be free of (111) twins. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evidence of a photon effect during the visible laser‐assisted deposition of polycrystalline silicon from silane

    Page(s): 1062 - 1064
    Save to Project icon | PDF file iconPDF (643 KB)  

    Silicon dots have been produced by the decomposition of silane on Si layers deposited on quartz plates and irradiated by a cw Ar+ laser beam. The vertical deposition rate of Si dots was investigated as a function of irradiation time, output laser power, and silane pressure. The Si layer on quartz was first irradiated with the laser beam penetrating through the transparent quartz plate (back irradiation). The deposition of Si dots occurred by pyrolytic decomposition of ‘‘cold’’ silane molecules impinging on the laser heated area. When the surface of the Si layer on quartz was directly irradiated with the visible laser beam (front irradiation), the deposition of Si dots was accomplished at lower temperatures and involved an interaction of photons with reactive species. The kinetics of this photon‐aided process is surface controlled and characterized by an apparent activation energy of about 38 kcal mol-1. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Laser‐assisted metalorganic molecular beam epitaxy of GaAs

    Page(s): 1065 - 1067
    Save to Project icon | PDF file iconPDF (628 KB)  

    We report preliminary studies of the growth of homoepitaxial GaAs by laser‐assisted metalorganic molecular beam epitaxy, using triethylgallium (TEGa) and As4 sources and a 193 nm ArF excimer laser. Laser irradiation results in a high, selective‐area growth rate at temperatures below 450 °C, where pyrolytic growth is very slow. The process is extremely efficient, with roughly unit probability for impinging TEGa molecules sticking and being dissociated by laser radiation to form GaAs. From the strong dependence on laser fluence, the growth enhancement process appears to be pyrolytic in nature (because of transient heating by the pulsed laser) and not photolytic. The cross section for photolysis must be at least ten times lower than the gas‐phase value (9×10-18 cm2). The surface morphology of films grown at 400 °C is rough at threshold fluences (∼0.10 J/cm2), but becomes smooth at higher fluences (∼0.13 J/cm2). These regions with relatively smooth surfaces exhibit enhanced photoluminescence yields compared to areas receiving less intense laser radiation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Chemical vapor deposition of a silicon nitride layer with an excellent interface by NH3 plasma treatment

    Page(s): 1068 - 1070
    Save to Project icon | PDF file iconPDF (344 KB)  

    A new metal‐insulator‐semiconductor field‐effect transistor (MISFET) fabrication technology has been developed by using a silicon nitride insulator. MISFET’s with high field‐effect mobility were obtained by exposing a silicon surface to a NH3 plasma before silicon nitride (SiNx) deposition as a gate insulator in a rf plasma. An Auger spectrum showed possible nitridation of silicon by NH3 plasma treatment. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Surface‐superlattice effects in a grating‐gate GaAs/GaAlAs modulation doped field‐effect transistor

    Page(s): 1071 - 1073
    Save to Project icon | PDF file iconPDF (431 KB)  

    We report transport phenomena exhibited by a two‐dimensional electron gas at the interface of a modulation doped GaAs/GaAlAs heterostructure in the presence of a field‐effect‐controlled periodic potential modulation. By means of x‐ray lithography and lift‐off, a 0.2‐μm‐period Schottky barrier grating gate was fabricated in lieu of the common continuous gate in a field‐effect transistor configuration. Conductance measurements at 4.2 K provide evidence of a superlattice effect. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hall effect in amorphous Si:H and amorphous Si:H/amorphous Ge:H superlattices

    Page(s): 1074 - 1076
    Save to Project icon | PDF file iconPDF (474 KB)  

    The sign anomaly in the Hall coefficient observed in substitutionally doped amorphous Si:H and amorphous Ge:H is also found in amorphous Si:H/Ge:H superlattices. The size of the Hall mobility in the superlattice is comparable to the Hall mobility in amorphous Si:H and amorphous Ge:H. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Generation of an anomalous hole trap in GaAs by As overpressure annealing

    Page(s): 1077 - 1079
    Save to Project icon | PDF file iconPDF (576 KB)  

    Deep levels in high‐purity n‐type molecular beam epitaxy (MBE) GaAs and in undoped n‐type metalorganic chemical vapor deposition (MOCVD) GaAs samples annealed with various As overpressures were investigated using constant capacitance deep level transient spectroscopy on evaporated Au Schottky barrier diodes. Anomalous hole traps, which could be measured because of a surface effect, were observed in all annealed samples. EL2 traps were created in the MBE material by the annealing, while the concentration of EL2 in the annealed MOCVD material was about the same as that before annealing. The effect of annealing on the other electron traps in these samples is also studied and reported. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Excitonic trapping from atomic layer epitaxial ZnTe within ZnSe/(Zn,Mn)Se heterostructures

    Page(s): 1080 - 1082
    Save to Project icon | PDF file iconPDF (735 KB)  

    ZnSe‐based structures have been fabricated, consisting of monolayers of ZnTe grown by atomic layer epitaxy spaced by appropriate dimensions to approximate a Zn(Se,Te) mixed crystal; this method has been used to overcome the difficulties encountered in the molecular beam epitaxy (MBE) of the alloy with a low Te concentration. Reported work has shown that blue‐blue/green luminescence, originating from exciton self‐trapping at Te sites in Zn(Se,Te) bulk crystal alloys, is significantly more intense than the light emitted from ZnSe. Luminescence originating from ZnTe‐containing ZnSe/ZnTe superlattice and ZnSe/(Zn,Mn)Se multiple quantum well structures was used to illustrate how the presence of ZnTe acts to trap excitons. Optical signatures of the MBE‐grown structures were similar to those of the random alloy, indicating that the exciton self‐trapping mechanism is important to the interpretation of recombination processes in structures containing ZnSe/ZnTe heterointerfaces. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Photorefractive imaging of semiconductor wafers

    Page(s): 1083 - 1085
    Save to Project icon | PDF file iconPDF (811 KB)  

    Making use of the photorefractive effect, we have developed a versatile method of imaging various crystal properties of semi‐insulating compound semiconductors. The magnitude and time evolution of refractive index gratings are monitored via diffraction. The observed diffraction is directly related to the electric fields present, and quantitative information concerning the spatial variation of dark conductivity, photoconductivity, and deep level absorption can be extracted. Wafers of undoped GaAs and InP:Fe have been characterized in this manner, and comparisons of images are made which demonstrate the capabilities of this technique. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Growth of low‐density two‐dimensional electron system with very high mobility by molecular beam epitaxy

    Page(s): 1086 - 1088
    Save to Project icon | PDF file iconPDF (656 KB)  

    We report on the growth of modulation‐doped GaAs/Alx Ga1-xAs heterostructures with mobilities (μ) on the order of 1×106 cm2 /V s (at 4.2 K) and areal densities (ns ) below 8×1010 cm-2 . In growing these structures we employ the atomic plane doping technique and ultrathick (≫1000 Å) spacer layers. The mobilities of these structures are the highest ever reported for low densities. Measurements of μ vs ns as a function of illumination or gate voltage indicate μ∼nαs behavior with α≂0.6 and, even for ns ≂1.4×1010 cm-2 , μ has a value in excess of 0.3×106 cm2 /V s. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • GexSi1-x strained‐layer heterostructure bipolar transistors

    Page(s): 1089 - 1091
    Save to Project icon | PDF file iconPDF (499 KB)  

    Double heterostructure bipolar transistors with the base region consisting of a p‐Ge0.5Si0.5 strained‐layer superlattice have been grown by molecular beam epitaxy. At a wavelength of 1.3 μm, optical gain as high as 52 has been achieved in two‐terminal phototransistors. The large photocurrent is inferred to be a product of the transistor gain, on the order of 20, and avalanche multiplication. A differential current gain of 10 has been obtained in the three‐terminal bipolar transistors. The incorporation of a narrow band‐gap GexSi1-x superlattice base is expected to result in higher emitter injection efficiency as compared to Si bipolar transistors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Investigation of point‐defect generation in silicon during oxidation of a deposited WSi2 layer

    Page(s): 1092 - 1094
    Save to Project icon | PDF file iconPDF (569 KB)  

    In recent letters it was reported from separate studies that silicidation of the refractory metals TaSi2 or TiSi2 on a silicon surface gives rise to injection of vacancy point defects into the underlying substrates. In both studies it was proposed that a vacancy influx may be induced by a silicon efflux during silicidation. In this work we show that during oxidation of WSi2 on silicon, which also causes an efflux of silicon atoms from the underlying substrate, no vacancy excess is observed based on monitoring diffusion of P and B buried marker layers. We also propose a possible explanation that reconciles the apparently discrepant findings that B diffusion is always retarded during vacancy supersaturations resulting from thermal nitridation reactions, while vacancy supersaturations observed during silicidation of TaSi2 result in enhanced diffusion of B. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Growth of highly oriented CdS thin films by laser‐evaporation deposition

    Page(s): 1095 - 1097
    Save to Project icon | PDF file iconPDF (549 KB)  

    CdS films have been grown by laser‐evaporation deposition in a clean vacuum environment. The films are highly oriented with a c axis perpendicular to the surface, and are optically smooth and homogeneous. These high quality films should be useful in nonlinear integrated optics applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • In situ preparation of Y‐Ba‐Cu‐O superconducting thin films by magnetron sputtering

    Page(s): 1098 - 1100
    Save to Project icon | PDF file iconPDF (573 KB)  

    Thin superconducting films of YBa2 Cu3 O7 have been prepared by magnetron sputtering from targets of sintered material in an oxygen‐argon atmosphere. The compositional and structural properties were studied by Rutherford backscattering and x‐ray diffraction. The films were deposited at substrate temperatures between 580 and 800 °C. It was found that the material grows in the oxygen deficient tetragonal phase. In situ heat treatment at 430 °C in pure O2 atmosphere generates the orthorhombic structure and the films on sapphire and SrTiO3 coated sapphire substrates show the full superconducting transition at 83 K. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electric properties of the YBa2Cu3O7-δ/Au interface

    Page(s): 1101 - 1102
    Save to Project icon | PDF file iconPDF (323 KB)  

    The electric properties of YBa2Cu3O7-δ/Au interfaces were investigated. An electric contact better than 108 Ω-1/cm2 was obtained at 4.2 K for the interface. There existed, however, a normal layer between the superconducting bulk and the gold electrode, preventing the observation of the proximity effect and the quasiparticle tunneling for this material. 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