bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular beam epitaxy growth method for vertical-cavity surface-emitting laser resonators based on substrate thermal emission
Authors: Talghader J. J. , Hadley M. A. , Smith J. S.
Published: July 2002

A molecular beam epitaxy growth monitoring method is developed for distributed Bragg reflectors and vertical-cavity surface-emitting laser (VCSEL) resonators. The wavelength of the substrate thermal emission that corresponds to the optical cavity resonant wavelength is selected by a monochromator and monitored during growth. This method allows VCSEL cavities of arbitrary design wavelength to be grown with a single control program. This letter also presents a theoretical model for the technique which is based on transmission matrices and simple thermal emission properties. Demonstrated reproducibility of the method is well within 0.1%.
Damage-induced luminescence in InP
Authors: Sekiguchi T. , Leipner H. S.
Published: July 2002

Optical properties of scratched InP specimens were studied by means of cathodoluminescence (CL). A new luminescence band around 942 nm (S1) was detected in the vicinity of scratches. The S1 band is composed of two peaks at 938 and 946 nm. Monochromatic CL images showed that the S1 luminescence is constrained to regions of high residual strain and not related to dislocations or cracks. The S1 intensity increased in samples with a higher Fe content. S1 vanished after 450 K annealing.
Effect of Cl incorporation on the stability of hydrogenated amorphous silicon
Authors: Byun Jae Seong , Jeon Hong Bin , Lee Kyung Ha , Jang Jin
Published: July 2002

Hydrogenated amorphous silicon (a-Si:H) films were prepared by remote plasma chemical vapor deposition (RPCVD) using SiH4/SiH2Cl2/He/H2 mixtures. With increasing Cl content in a-Si:H up to about 1019 cm−3, the stablity of photoconductivity under light illumination was improved with keeping the defect density and Urbach energy constant. We deposited hydrogenated amorphous silicon films with hydrogen content of 6 at. %, Cl content of ∼1019 cm−3, and defect density of 3×1015 cm−3, which exhibited very small photoconductivity degradation under light illumination. The optimum Cl concentration in a-Si:H for stable a-Si:H appears to be ∼1019 cm−3.
A ytterbium- and neodymium-co-doped yttrium aluminum garnet–buried channel waveguide laser pumped at 0.81 μm
Authors: Sugimoto N. , Ohishi Y. , Katoh Y. , Tate A. , Shimokozono M. , Sudo S.
Published: July 2002

In this paper we will explain the preparation of an epitaxially grown ytterbium- and neodymium-co-doped yttrium aluminum garnet [(Yb,Nd):YAG]–buried channel waveguide laser on a YAG substrate. Waveguides, whose cores are formed with Ar ion beam etching, demonstrate single-mode operation. The (Yb,Nd):YAG waveguide laser operates at 1.03 μm when pumped at 0.81 μm, as a result of a nonradiative energy transfer from Nd3+ ions to Yb3+ ions. The incident threshold and slope efficiency of the 5 mm long waveguide laser are 235 mW and 13%, respectively. Output power of 50 mW is obtained for an incident power of 620 mW at room temperature.
Surface acoustic wave reflections from a proton exchanged dispersive dot array
Authors: Tuli Suneet , Bhattacharyya A. B. , Fournier D.
Published: July 2002

Proton-exchanged (PE) regions in LiNbO3 create an invisible inhomogeneity that can be used as surface acoustic wave (SAW) reflectors similar to metallized overlays, implanted layers, or grooves. We report the detection of coherently reflected SAW, from a dispersive array of proton-exchanged dot rows, by utilizing a sensitive interferometric heterodyne laser probe.
Blocking injected dark current in impurity-band-conduction photodetectors using a PtSi Schottky barrier
Authors: Martin B. G. , Fathauer R. W. , Jones E. W. , Krabach T. N. , Dejewski S. M.
Published: July 2002

An experimental investigation was made on the use of a PtSi Schottky barrier for blocking injected electron dark current in a back-illuminated impurity-band-conduction (IBC) photodetector, a device used for detecting long-wavelength infrared (LWIR) radiation. Measured results on the Schottky barrier height as well as current versus applied bias results are presented, and show that the desired blocking capability has been attained. At the low operating temperatures (∼10 K) of the IBC device, the injected dark current is below our measurement capability for applied biases of up to 10 V. Injected dark current in conventional devices occurs at biases of ∼1 V. The modified device configuration discussed here would enable one to store the mobile ionized donor charge for subsequent readout.
Threshold characteristics of planar and index-guided microcavity lasers
Authors: Huffaker D. L. , Deppe D. G. , Shin J.
Published: July 2002

Lasing threshold modes are studied experimentally for microcavity lasers fabricated to operate either as planar cavities, in which the mode is established by the emitter distribution, or as index-guided modes in the planar cavity with weak three-dimensional confinement. For no lateral index guiding, the lasing mode area is suggested to depend on the gain saturation. For lateral index confinement to a small area, spectral and radiation pattern measurements show that the spontaneous emission coupling is increased, and reduces the lasing threshold even in the presence of an increased loss.
InP/InGaAs photodetector based on a high electron mobility transistor layer structure: Its response at 1.3 μm wavelength
Authors: Horstmann M. , Marso M. , Fox A. , Rüders F. , Hollfelder M. , Hardtdegen H. , Kordos P. , Lüth H.
Published: July 2002

We report on the investigation of the room-temperature optoelectronic behavior of a metal–semiconductor–metal two-dimensional electron gas photodiode based on the two-dimensional electron gas of a high electron mobility transistor structure. The photodetector is fabricated in the InP/InGaAs material system, without use of Al-containing layers. Optoelectronic measurements on a device with a finger spacing of 3 μm show a full width at half-maximum (FWHM) of the pulse response of ≤60 ps, which is the resolution limit of our measurement equipment. Low-temperature measurements at 40 K with electro-optical sampling at a wavelength of 890 nm show a FWHM of 1 ps.
Effect of dislocation reduction via strained InGaAs interlayers in GaAs grown on Si(001)
Authors: Uchida Yoko , Yazawa Yoshiaki , Warabisako Terunori
Published: July 2002

The effects of strain and In content on dislocation reduction was studied by introducing an InGaAs strained layer into a GaAs layer on a Si substrate. The two effects were separated by using the strain energy that accumulates in the InGaAs layer, since the strain in an InGaAs layer varies with In content. The results show that the variation in dislocation density depends on the strain and not on the In content. A strain energy of 250 dyn/cm was sufficient for effectively reducing dislocations in both the InGaAs layer and in the GaAs overlayer. However, when the strain energy was over 500 dyn/cm, the number of dislocations increased when an InGaAs layer was introduced.
Kinetics of Si1−xGex/Si(0≤x≤1) growth by molecular beam epitaxy using disilane and germanium
Authors: Zhang F. C. , Singh J. , Bhattacharya P. K.
Published: July 2002

Molecular beam epitaxy of Si1−xGex alloys, using gaseous Si2H6 and solid Ge as sources, has been studied over the entire composition range (0≤x≤1). From the measured growth rates as a function of x, it is clear that the presence of Ge tends to decrease the Si incorporation rate. This establishes growth via adatom migration to kink sites in a dissociative chemisorption process.
Efficient lateral minority carrier transport in proton-implanted p-type silicon
Authors: Leung D. C. , Nelson P. R. , Stafsudd O. M. , Parkinson J. B. , Davis G. E.
Published: July 2002

A highly efficient lateral transport mechanism has been observed in stable defect layers (SDL) in p-type silicon. The SDLs were produced by proton implantation followed by rapid thermal anneal. Photogenerated carriers have been collected at a Schottky junction several millimeters away from the generation site. This transport distance is more than 30 times the diffusion length in comparable bulk material. A model is proposed in which bending of the energy bands near the SDL expels majority carriers, leaving no substantial recombination mechanism for minority carriers trapped in the layer.
Three-photon photoemission from GaAs–O–Cs negative electron affinity surfaces induced by 2.06 μm nanosecond laser pulses
Authors: Wang Liming , Cheng Zhao , Ping Qi , Hou Xun
Published: July 2002

Three-photon photoemission effect on GaAs–O–Cs negative electron affinity surfaces (NEA) was studied by using a nanosecond pulsed laser at 2.06 μm wavelength. The photocurrent densities from the photocathodes with different sensitivities were measured as a function of laser intensity at both room and liquid nitrogen temperatures (77 K). The dependence of photocurrent density on the light intensity shows a typical slope of three in logarithmic plot. The results are interpreted in terms of multiphoton photoemission (MPPE) effect. The influence of thermal electron emission to MPPE are discussed.
High transport critical currents in flexible screen-printed Ag-(Bi,Pb)2Sr2Ca2Cu3Ox tapes
Authors: Oota A. , Ogawa K. , Maeda J. , Shibata K.
Published: July 2002

We fabricated screen-printed Ag-(Bi,Pb)2Sr2Ca2Cu3Ox monofilament and multifilament tapes with filament number 1≤N≤5. As N increases, the critical current Ic increases monotonically until it reaches 54 A (77 K, 0 T) for N=5, while the critical current density Jc is around 1.6×104 A/cm2 (77 K, 0 T) nearly independent of N. The bend strain tolerance is found to decrease with increasing N. For monofilament tapes the strain tolerance is 2%–3% strain while for multifilament tapes it decreases to ∼1% at N=3 and ∼0.4% at N=5.
Time-bandwidth product of gain-switched In0.2Ga0.8As/GaAs microcavity lasers
Authors: Michler P. , Rühle W. W. , Reiner G. , Ebeling K. J. , Moritz A.
Published: July 2002

We present the temporal and spectral evolution of stimulated emission from In0.2Ga0.8As/GaAs microcavity laser samples at 20 K after femtosecond optical excitation. Both, linewidth and chirp become smaller when the cavity resonance is at shorter wavelengths within the gain spectrum of the quantum well: The linewidth is reduced from Δλ=0.41 nm at 923 nm, where the threshold is lowest, to Δλ=0.26 nm at 884 nm. Comparison with a phenomenological model yields linewidth enhancement factors α of 2 and 5 for emission wavelengths of 884 and 925 nm, respectively. A time-bandwidth product of 0.68 is obtained at the shorter wavelength.
Electro-optic modulation and self-poling in strain-induced waveguides in barium strontium titanate niobate
Authors: Marx J. M. , Eknoyan O. , Taylor H. F. , Tang Z. , Neurgaonkar R. R.
Published: July 2002

Characterization of bulk single crystals and optical waveguides in Ba1−xSrxTiyNb2−yO6 (BSTN) indicate it to be a promising new ferroelectric material for electrooptic devices. The electro-optic coefficient r33 is measured to be 218±12 pm/V, a factor of 7 greater than LiNbO3. Data on refractive indices, dielectric constant, and Curie temperature Tc in bulk samples are also presented. Strain-induced waveguides in Z-cut samples exhibited low losses (1.8 dB/cm for TM polarization and 2.5 dB/cm for TE polarization) at a wavelength of 1.3 μm. Electro-optic modulation was demonstrated in these waveguides to frequencies ≳100 MHz. A ‘‘self-poling’’ effect was found, whereby strong electro-optic modulation is observed in the strain waveguides without repoling the crystal after processing at temperatures far above Tc.
High optical quality of strained (111)B In0.12Ga0.88As/GaAs and In0.12Ga0.88As/Al0.2Ga0.8As multiple quantum wells
Authors: Chin Albert , Lin B. C.
Published: July 2002

We have investigated the growth of high quality In0.12Ga0.88As/GaAs and In0.12Ga0.88As/Al0.25Ga0.75As multiple quantum wells (MQWs) on 1° misoriented (111)B and (100)GaAs substrates. Very narrow photoluminescence (PL) linewidths of 6.6 and 5.6 meV were measured in (100) and (111)B In0.12Ga0.88As/GaAs MQWs, respectively, which indicates the good optical quality of materials. In addition, more than an order of magnitude enhancement of PL intensity was measured from the (111)B sample relative to that from (100), which is consistent with the previously reported strongly enhanced optical property in (111)B AlGaAs/GaAs QW to (100). In contrast, under our normal growth conditions, narrow PL linewidth and large PL intensity were difficult to achieve in (111)B In0.12Ga0.88As/Al0.25Ga0.75 As MQWs. Two-step growth with a high AlGaAs growth temperature was used to improve the optical quality of (111)B In0.12Ga0.88As/Al0.25Ga0.75 As MQWs. A narrow PL linewidth of 5.1 meV and four times enhanced PL intensity can be obtained by such two-step growth. Cross-sectional transmission electron microscopy indicates defects generated in the 550 °C grown (111)B In0.12Ga0.88As/Al0.25Ga0.75 As MQWs, while such defects were reduced or disappeared at a high AlGaAs growth temperature of 620 °C.
Monolithic integration of quantum well infrared photodetector and modulator
Authors: Almogy Gilad , Xu Yuanjian , Tong Andrew , Shakouri Ali , Yariv Amnon
Published: July 2002

A modulation depth of 40% (0.7 dB/μm) was obtained with an infrared (10.6 μm) modulator consisting of a stack of 50 pairs of weakly coupled asymmetric quantum wells monolithically integrated with a quantum well infrared photodetector. The monolithic integration is shown to be a promising technique for the ‘‘ac’’ coupling of infrared focal-plane arrays as well as for the direct study of the effects of electric fields and charge density variations on intersubband transitions.
Transmission zero engineering in lateral double-barrier resonant tunneling devices
Authors: Shao Zhi-an , Porod Wolfgang , Lent Craig S.
Published: July 2002

Transmission zero engineering in lateral double-barrier resonant tunneling devices is investigated. We show that, by inserting a resonant cavity in the quantum well region of a lateral double-barrier resonant tunneling structure and engineering the placement of transmission zero-pole pairs, the current peak-to-valley ratio of the device can be drastically improved at low temperature. An advantage of this structure also is that a lower peak voltage can be obtained compared to the corresponding lateral double-barrier resonant tunneling device.
Sealing AlAs against oxidative decomposition and its use in device fabrication
Authors: Huffaker D. L. , Deppe D. G. , Lei C. , Hodge L. A.
Published: July 2002

Data are presented demonstrating that an exposed AlAs layer can be sealed against further decomposition as would otherwise occur due to, for example, wet oxidation. A critical processing step consists of a brief 500–600 °C anneal in forming gas of a previously room ambient exposed AlGaAs surface. In the brief high-temperature anneal, a thin but dense surface barrier layer forms which further blocks diffusing oxygen species. The effectiveness of the surface layer as a barrier is demonstrated through its use as a mask against wet oxidation in the fabrication of an all-epitaxial selectively oxidized multimode AlAs/AlGaAs vertical-cavity laser.
Crystal structure and magnetic properties of LaCo10Al3
Authors: Guo Yongquan , Liang Jingkui , Tang Weihua , Zhao Yanming , Rao Guanghui
Published: July 2002

The crystal structure and magnetic properties of a LaCo10Al3 intermetallic compound have been investigated by x-ray powder diffraction and magnetic measurement. The space group of the LaCo10Al3 structure is I4/mcm, which can be derived from the cubic NaZn13-type structure. Each unit cell contains four formula units of LaCo10Al3. The lattice parameters are a=8.085(1) Å, c=11.624(8) Å, and the calculated density is Dx=7.07(3) g/cm3. In each unit cell, there are five kinds of equivalent positions, i.e., 4a, 16l(1), 16k 16l(2), and 4d, which are occupied by 4La, 16Co(1), 16Co(2), 16(Co+Al) and 4Co(3) atoms, respectively. The tetragonal LaCo10Al3 intermetallic compound is ferromagnetic with a Curie temperature of 840 K. The magnetic moment per Co atom is 0.84μB, which can be explained by the magnetic valence model.
Anisotropic self-field effect in a-axis YBa2Cu3O7−x/Ag/PbIn Josephson junctions
Authors: Takeuchi I. , Lobb C. J. , Trajanovic Z. , Warburton P. A. , Venkatesan T.
Published: July 2002

We have measured magnetic diffraction patterns of critical currents of vertical geometry YBa2Cu3O7−x(YBCO)/Ag/PbIn Josephson junctions made with in-plane aligned a-axis oriented YBCO films. Anisotropic penetration depths in YBCO and the resulting Josephson penetration depths give rise to diffraction patterns which are distinctly different when the magnetic field is applied in two orthogonal directions (b and c). The London penetration depths of YBCO, λb, and λc, are found to be ∼2000 Å and ∼1.2 μm, respectively, at 4.2 K. Intrinsic IcRn products of up to 0.2 mV have been obtained in these junctions.
Study of double barrier superlattice by synchrotron radiation and double-crystal x-ray diffraction
Authors: Zhuang Y. , Wang Y. T. , Jiang D. S. , Yang X. P. , Jiang X. M. , Wu J. Y. , Xiu L. S. , Zheng W. L.
Published: July 2002

An (AlAs/GaAs/AlAs/AlGaAs)/GaAs(001) double-barrier superlattice grown by molecular beam epitaxy (MBE) is studied by combining synchrotron radiation and double-crystal x-ray diffraction (DCD). The intensity of satellite peaks is modulated by the wave function of each sublayer in one superlattice period. Simulated by the x-ray dynamical diffraction theory, it is discovered that the intensity of the satellite peaks situated near the modulating wave node point of each sublayer is very sensitive to the variation of the layer structural parameters. The accurate layer thickness of each sublayer is obtained with an error less than 1 Å. Furthermore, x-ray kinematical diffraction theory is used to explain the modulation phenomenon.
Adatom migration effects during molecular beam epitaxial growth of InGaAs/GaAs quantum wells on patterned substrates with vertical sidewalls: Blue shift in luminescence spectra
Authors: Phillips J. , Kamath K. , Singh J. , Bhattacharya P.
Published: July 2002

We have studied the blue shift in photoluminescence emission energy of pseudomorphic InGaAs/GaAs quantum wells grown on patterned (001) GaAs substrates with grooves and trenches having vertical sidewalls made by dry etching. Dependence of the blue shift, which can be as large as 51 meV, on the direction, feature size, and the etch depth of the patterns as well as the thickness of the buffer layer was observed, and is explained by the altered migration behavior of the adatoms.
Electroluminescence from forward-biased Er-doped GaP p-n junctions at room temperature
Authors: Ford G. M. , Wessels B. W.
Published: July 2002

The electroluminescent properties of Er-doped GaP light emitting diodes are reported. Diodes were prepared by metalorganic vapor phase epitaxy and zinc diffusion. Strong characteristic Er3+ emission at 0.80 eV (1.54 μm) under forward bias is detected at room temperature. Minimal thermal quenching of the electroluminescence was observed. The luminescence intensity depended linearly on current density for low applied current densities, and saturated at a current density of 17 A/ cm2
Coimplantation of carbon and group II acceptors in GaAs
Authors: Morton R. , Lau S. S. , Poker D. B. , Chu P. K.
Published: July 2002

Coimplantation of carbon and one of the group II acceptors Mg, Zn, or Cd, was performed in GaAs using doses of 5×1014 cm−2, and the resulting p-type electrical activity was studied. Carbon and group II coimplantation offers a means of maintaining the III–V stoichiometry, which is known to be beneficial for both carbon and group II activation. The group II implantation profiles show reduced diffusivity from the balance in stoichiometry the carbon coimplantation provides. The group II elements Zn and Cd create substantial implantation damage and therefore help assist carbon activation by supplying the necessary abundance of As vacancies. The Mg coimplantation, because of the light mass of the ion, does not create a significant amount of lattice damage at this dose and consequently the implanted carbon remains inactive, which results in reduced conductivity. This investigation differs from past group III and carbon coimplantation studies because both of the coimplanted species, the group II and carbon, contribute to p-type conductivity as well as help to maintain the stoichiometry.
Thickness measurements of Si1−xGex layers on Si mesa structures using Raman spectroscopy
Authors: Wasserman A. , Roth D. J. , Beserman R. , Hoffman A. , Dettmer K.
Published: July 2002

A Si0.6Ge0.4 layer has been deposited on a patterned Si substrate containing mesas of width ranging from 2 to 200 μm. Raman spectra at various points on the sample were taken, and evaluation of layer thickness has been performed, showing different values in different areas of the mesas. This can be explained as being a consequence of the different growth rates on different crystal planes. The stress was measured from Raman shift, and was found to be constant within the 0.7 μm diameter spot of the laser. Dependence of the thickness on mesa width was not found.
On the impact of interface energy and vacancy concentration on morphology changes and nucleation of silicon oxide precipitates in silicon
Authors: Vanhellemont Jan
Published: July 2002

An expression for the critical radius for growth of spherical precipitates is used to estimate the interface energy between silicon oxide precipitates and the surrounding silicon matrix from observations on precipitate morphology changes. The calculated interface energy is one order of magnitude larger than values commonly accepted but corresponds well with those measured on bonded wafers. The important impact of the vacancy concentration on the critical radius is stressed and allows an understanding of the apparent difference. Implications for balling up of oxide layers embedded in silicon and for oxygen precipitate nucleation during crystal pulling are also addressed.
Formation of rare-earth oxide doped silicon by spark processing
Authors: St. John John V. , Coffer Jeffery L. , Gyu Rho Young , Pinizzotto Russell F.
Published: July 2002

In this work, we report a method for the incorporation of rare-earth oxides onto silicon surfaces. This process uses a high-energy dc spark to convert salts of rare-earth ions such as europium and erbium to the corresponding oxide phase(s) with concomitant formation of a porous layer. Scanning electron micrographs of the silicon substrate show an irregular, pitted surface morphology for those areas exposed to spark processing. Photoluminescence, infrared spectroscopy, and electron microscopy of the spark-processed regions of the Si substrate are clearly consistent with the formation of the desired luminescent oxide phase.
Change in bulk defect density of hydrogenated amorphous silicon by bias stress in thin film transistor structures
Authors: Park Hyuk-Ryeol , Oh Dong-Sun , Jang Jin
Published: July 2002

The changes in defect density of hydrogenated amorphous silicon (a-Si:H) in thin film transistor (TFT) structures by prolonged bias stress or light soaking have been studied through constant photocurrent method (CPM) measurements. The CPM absorptions due to defect absorptions do not change after positive or negative bias-stress. On the other hand, the CPM absorptions due to dangling bond defects increase remarkably after light soaking. These experimental results demonstrate that the bulk defect density of a-Si:H in TFT structure is not changed after long time bias stress even though the characteristics of the TFT degrade significantly.
Operation and stability of antiguided flared amplifiers
Authors: Ramanujan S. , Winful H. G.
Published: July 2002

We present a propagation model for the dynamics of antiguided flared amplifiers. This model takes into account diffraction, carrier diffusion, spatial hole burning, carrier-induced antiguiding, and spontaneous emission. Numerical results demonstrate that flared antiguides are significantly less susceptible to noise induced filamentation than broad area devices.
Neutron-capture-induced radiation treatment of polymeric materials
Authors: Rej Donald J. , Pickrell Mark M. , Wrobleski Debra A.
Published: July 2002

A method for the bulk treatment of polymeric materials is proposed. Energetic ions created after capture of a neutron beam by constituent atoms located within the polymer can be used to cause radiation-induced modifications such as cross linking in the polymer. In contrast to traditional ion implantation, the proposed method enables bulk treatment because of the relatively deep penetration of neutrons. Analytical estimates and Monte Carlo computations are performed for the 10B(n,α)7Li reaction for the cross linking and hydrogen depletion of boron-doped polystyrene. Requirements for the polymer composition and microstructure, as well as potential synthesis methods are discussed.
Waveguiding in (quantum) wire structures: Impact on the polarization characteristics and the slope of the optical gain
Authors: Lehr G. , Härle V. , Scholz F. , Schweizer H.
Published: July 2002

This work discusses the role of quantum wires as electromagnetic waveguides. The optical gain of buried InGaAs/In(GaAs)P wire structures is investigated as a function of the wire width. We find that the relative contribution of the light and heavy hole transition as well as the optical polarization of the gain are strongly dependent on the wire width. This corresponds to the behavior expected as a result of quantum confinement. Based on calculations of the waveguiding behavior of the wires, however, we attribute these effects to changes of the waveguide properties rather than to quantum confinement effects of the carriers.
Role of heterointerface on enhancement of no-phonon luminescence in Si-based neighboring confinement structure
Authors: Usami N. , Shiraki Y. , Fukatsu S.
Published: July 2002

The origin of the no-phonon (NP) luminescence enhancement was explored in Si-based neighboring confinement structures (NSCs). Post growth annealing was found to lead to quenching of the NP line. Time-resolved photoluminescence study clarified that the radiative lifetime of the annealed sample increases with increasing temperature, while that of the as-grown sample shows no significant change at low temperatures (<40 K). These results are reasonably explained by considering that ‘‘in-plane’’ exciton at the heterointerface is the controlling mechanism for the NP enhancement which is observed at low temperatures in the as-grown NCS.
Observation of a new type of plasma etching damage: Damage to N-channel transistors arising from inductive metal loops
Authors: Salah A. , Awadelkarim O. O. , Preuninger F. , Chan Y. D.
Published: July 2002

We report a new type of damage, referred to here as inductive damage, induced by metal 1 plasma etching. The devices used in this study are lightly doped drain n-channel metal–oxide semiconductor field effect transistors (MOSFETs) fabricated on 200 mm p/p+ silicon wafers. The channel lengths of the investigated transistors are 0.5 μm with 90 Å thick thermally grown gate oxides. The metal 1 main etch (duration 30 s) and overetch (50%) employed BCl3/N2/Cl2 chemistry and was done using a standard reactive ion etching tool operated at rf power of 600 W and rf frequency of 13.56 MHz. Specially designed MOSFETs with inductive metal loops connecting the gate and substrate or the gate and drain are used to examine inductive damage. Inductive damage is shown to arise from electrical stress of the gate oxide and oxide/Si interface by the electromotive force generated in the metal loops by the metal plasma etch.
The influence of impurities on the dislocation behavior in heteroepitaxial ZnSe on GaAs
Authors: Kalisetty S. , Gokhale M. , Bao K. , Ayers J. E. , Jain F. C.
Published: July 2002

We have studied the influence of impurities on the dislocation behavior in heteroepitaxial layers of ZnSe on GaAs, grown by photoassisted organometallic vapor phase epitaxy. In undoped ZnSe layers, the dislocation densities are similar to those obtained by [S. Akram, H. Eshani, and I. B. Bhat, J. Cryst. Growth 124, 628 (1992)] whose data show that there is an inverse relationship between layer thickness and dislocation density. Incorporation of the electronically active impurity Cl increases the dislocation densities relative to undoped layers of the same thickness. Also, there is a correlation between the normalized dislocation density and the concentration of incorporated Cl. The isoelectronic impurity Cd has a similar effect on the dislocation density. Incorporation of Cd to a concentration of ∼1020/cm3 increases the dislocation density by a factor of about 3 compared to undoped layers of equal thickness. We also observed that doping of both Cd and Cl together resulted in low dislocation densities similar to the undoped case. Based on our results, we believe that the controlling factor for this phenomenon is the absolute value of the tetrahedral misfit for the impurity, rather than its sign, or the electronic activity of the impurity, or the sublattice on which the impurity resides. We propose an ‘‘impurity hardening’’ model to explain these results. According to this model the glide of dislocations is inhibited by the addition of impurities due to the local strain fields around the substitutional sites. The higher dislocation densities observed here with doping are an indirect result of impurity hardening. However, for single crystals or pseudomorphic heteroepitaxial layers, impurity hardening can inhibit the introduction of dislocations.
Tunneling and anisotropic charge transport properties of superconducting (110)-oriented YBa2Cu3O7 thin films
Authors: Covington M. , Scheuerer R. , Bloom K. , Greene L. H.
Published: July 2002

We have measured the tunneling conductance of YBa2Cu3O7/Pb planar tunnel junctions fabricated on superconducting (110)-oriented YBa2Cu3O7 thin films exhibiting zero-resistance superconducting transition temperatures (Tc’s) between 88 and 89.5 K. The conductance is the same as we and other groups have measured on (100)- and (103)-oriented YBa2Cu3O7/Pb junctions and quantitatively different from c-axis tunneling. The ab-plane transport is comparable to that measured in (001)-oriented YBa2Cu3O7 thin films, and the transport anisotropy varies between 65 and 80 from 300 K to Tc, respectively. This anisotropy is higher than that previously measured in both (110)-oriented and c-axis aligned (100)-oriented films, but it is comparable to that measured in single crystals.
Demonstration of the formation of four-wave mixing interaction regions in a high-efficiency mutually pumped phase conjugator
Authors: Zhang Liangmin , Zhang Jingwen , Shao Zongshu , Mu Xiaodong , Chen Huanchu , Jiang Minhua
Published: July 2002

We show a mutually pumped phase conjugator with a high coupling efficiency in a novel crystal of copper-doped potassium sodium strontium barium niobate. A twisting around of one another and self-curving coupling channel is observed. A theory is developed to simulate the coupling channel. The shape of curved trajectories has also been calculated. We verify that one, two, three, and more four wave mixing interaction regions exist in photorefractive bridge mutually pumped phase conjugators with the simulations. The calculated results are essentially consistent with our experimental observations, and they may be used in other photorefractive phase conjugators after making a modification.
Point contact ultrasonic transducer of waveguiding structure for high-frequency operation
Authors: Yamada Ken , Khuri-Yakub Butrus T.
Published: July 2002

This letter presents a new type of Hertzian-contact transducer of waveguiding structure operating in the MHz range. The transducer is composed of a fused quartz tube and a radially-polarized annular piezoelectric element bonded to one of its ends. The edge-bonded shear-wave transducer effectively excites a surface wave on the interior surface of the tube. A small bullet pin made of quartz is inserted and fixed on the other end of the tube to make a point contact and transmit the wave energy to a specimen to be inspected. Using a pair of these transducers, we have succeeded in exciting and detecting surface acoustic waves as well as Lamb waves in the 3 MHz frequency range.
Boron-compensation effect on hydrogenated amorphous silicon with oxygen and nitrogen impurities
Authors: Isomura Masao , Kinoshita Toshihiro , Tsuda Shinya
Published: July 2002

Oxygen and nitrogen impurities increase the dark conductivity of hydrogenated amorphous silicon (a-Si:H), due to their donorlike behavior. An appropriate amount of boron doping recovers these values to the original ones unless the effect of band gap widening appears. The midgap absorption spectra of the compensated a-Si:H are identical to those of intrinsic a-Si:H both at initial and light-soaked states. The major effect of the oxygen and nitrogen is the creation of donors, which show a similar behavior to those by phosphorus—only a small fraction of the oxygen and nitrogen produces donors, the rest is included in the a-Si:H network without causing any other significant effect until alloying effects appear.
Scanning-tunneling-microscopy modification of nitrogen-passivated GaAs (001) surfaces on a nanometer scale
Authors: Kasu Makoto , Makimoto Toshiki , Kobayashi Naoki
Published: July 2002

Using scanning tunneling microscopy (STM), we perform nanometer-scale modifications on nitrogen (N)-passivated GaAs (001) surfaces. After the surface is passivated with nitrogen gas through a heated tungsten filament in an ultrahigh-vacuum chamber, STM modification is performed by increasing the tunnel current. A 200×200 nm2 square groove was successfully fabricated. The smallest grooves are 0.5 nm deep and 5 nm wide when sample bias is −3 V and tunnel current is 5 nA. The threshold current for modification is 5 nA for surfaces with N passivation, but more than 50 nA for surfaces without N passivation.
Preferential alignment of Er–2O centers in GaAs:Er,O revealed by anisotropic host-excited photoluminescence
Authors: Hogg R. A. , Takahei K. , Taguchi A. , Horikoshi Y.
Published: July 2002

When GaAs is co-doped with Er and O by metalorganic chemical vapor deposition, the host-excited photoluminescence (PL) is dominated by 4I13/2→4I15/2 intra-4f-shell luminescence (1.54 μm) from a center identified as an Er atom substituting for Ga, coupled with two O atoms (Er–2O). The preferential alignment of the Er–2O center is revealed by the optical anisotropy exhibited by such samples when detecting host-excited PL polarized parallel to the 〈110〉 crystallographic directions. The preferential alignment of a specific symmetry axis of the Er–2O center is determined to be along the growth direction, [001]. This observation contrasts previous work on rare-earth (RE) doped materials where the RE luminescence center itself exhibits anisotropic luminescent properties, but a random distribution of differently oriented centers results in isotropic host excited PL.
Generation and detection of transverse ultrasonic waves via vortex tilting in superconductive YBa2Cu3O7
Authors: Haneda H. , Ishiguro T. , Murakami M.
Published: July 2002

A rf magnetic field applied to the high-Tc superconductor YBa2Cu3O7 under a crossed dc magnetic field generates a transverse ultrasonic wave, associated with the tilt of pinned vortices. The reverse situation, in which the rf field is generated by the application of the ultrasonic wave, also exists. The polarization of the transverse ultrasonic wave is parallel to the rf field. Experimental results related to line and Josephson vortices are presented as functions of temperature and magnetic fields.
Length scaling of bandwidth and noise in hot-electron superconducting mixers
Authors: Burke P. J. , Schoelkopf R. J. , Prober D. E. , Skalare A. , McGrath W. R. , Bumble B. , LeDuc H. G.
Published: July 2002

Mixing experiments have been performed at frequencies from 4 to 20 GHz on Nb thin-film superconducting hot-electron bolometers varying in length from 0.08 to 3 μm. The intermediate frequency (IF) bandwidth is found to vary as L−2, with L the bridge length, for devices shorter than √12 Le−ph≊1 μm, with Le−ph the electron-phonon length. The shortest device has an IF bandwidth greater than 6 GHz, the largest reported for a low-Tc superconducting bolometric mixer. The conversion efficiencies range from −5 to −11 dB (single sideband, SSB). For short bridges, the mixer noise temperature is found to be as low as 100 K (double sideband, DSB), with little length dependence. The local oscillator power required is small, ≊10 nW. Such mixers are very promising for low-noise THz heterodyne receivers.
Nanofabrication of sensors on cantilever probe tips for scanning multiprobe microscopy
Authors: Luo K. , Shi Z. , Lai J. , Majumdar A.
Published: July 2002

A simple method for nanofabricating sensors on cantilever probe tips, used in atomic force microscopy (AFM), is described. The method uses voltage pulses to evaporate and create a nanometer-scale hole at the very end of a metallized AFM cantilever probe tip. The hole in the metal film can be used as a mask for further device fabrication. We demonstrate this by fabricating a nanothermocouple junction on the probe tip. Thermal images of electrically heated patterned metal lines obtained by this probe suggest the spatial resolution to be about 10 nm. Fabrication of nanosensors on probe tips is likely to assist in the future development of scanning multiprobe microscopy.
9.6 μm wavelength mixing in a patterned YBa2Cu3O7-δ thin film
Authors: Trifonov V. A. , Karasik B. S. , Zorin M. A. , Gol’tsman G. N. , Gershenzon E. M. , Lindgren M. , Danerud M. , Winkler D.
Published: July 2002

Hot-electron bolometric (HEB) mixing of 9.6 μm infrared radiation from two lasers in high-quality YBa2Cu3O7−δ (YBCO) patterned thin film has been demonstrated. A heterodyne measurement showed an intermediate frequency (IF) bandwidth of 18 GHz, limited by our measurement system. An intrinsic limit of 100 GHz is predicted. Between 0.1 and 1 GHz intermediate frequency, temperature fluctuations with an equivalent output noise temperature Tfl up to ∼150 K, contributed to the mixer noise while Johnson noise dominated above 1 GHz. The overall conversion loss at 77 K at low intermediate frequencies was measured to be ∼25 dB, of which 13 dB was due to the coupling loss. The HEB mixer is very promising for use in heterodyne receivers within the whole infrared range.
Emission dynamics of In0.2Ga0.8As/GaAs λ and 2λ microcavity lasers
Authors: Michler P. , Hilpert M. , Rühle W. W. , Wolf H. D. , Bernklau D. , Riechert H.
Published: July 2002

We study the emission dynamics of two In0.2Ga0.8As/GaAs microcavity lasers after femtosecond optical excitation at 20 K. The pulse widths and the peak delays of λ and a 2λ cavity are compared. Pulses as short as 3.3 ps (9.5 ps) and peak delays as short as 8.2 ps (16.5 ps) are obtained with the 2λ cavity (λ cavity). The pulse widths and peak delays are well described by a model based on a rate equation analysis for carrier and photon densities; in particular, the better high speed characteristics of the 2λ cavity compared to the λ cavity are well reproduced.
Self-focusing Rayleigh wave using a time reversal mirror
Authors: Ing R. K. , Fink M. , Casula O.
Published: July 2002

Detection of surface and subsurface flaws is achieved using the time reversal process leading to self-focusing Rayleigh waves. The generation of surface waves is accomplished with an array of transducers coupled to the specimen with a Plexiglas wedge. The advantages of this technique are demonstrated with the detection of surface and subsurface holes of subwavelength dimensions. An optical interferometer is used to control the surface acoustic field obtained with such a time reversal process.
Incorporation of hydrogen in nitrogen and arsenic doped ZnSe epitaxial layers grown by organometallic vapor phase epitaxy
Authors: Bourret-Courchesne Edith D.
Published: July 2002

The incorporation of hydrogen has been investigated using secondary ion mass spectroscopy in arsenic and nitrogen doped ZnSe epitaxial layers grown by organometallic vapor phase epitaxy in a metalhydride free environment. Diisopropylselenide, diethylzinc, tertiarybutylarsine, and tertiarybutylamine were used as precursors. Ammonia was used to provide comparative data for the analysis of the results obtained with tertiarybutylamine. The carrier gas was either hydrogen or nitrogen. The arsenic doped samples grown in nitrogen carrier gas have a low concentration of hydrogen while hydrogen is incorporated in large quantity in samples grown with hydrogen carrier gas. High concentrations of nitrogen are obtained with tertiarybutylamine at low growth temperature and with hydrogen carrier gas. Low concentrations of nitrogen are obtained with tertiarybutylamine in presence of nitrogen carrier gas. Hydrogen incorporation is reduced when using tertiarybutylamine instead of ammonia as dopant source.
The shape of a nanoprobe determined by imaging spherical clusters
Authors: Sumetskii M. , Kornyshev A. A. , Stimming U.
Published: July 2002

We suggest a method to restore the shape of the tip of a scanning probe microscope at the nanometer scale by averaging images of spherical clusters distributed along the sample surface and present the corresponding theoretical framework for the treatment of experimental data.
Analysis of capacitance-voltage characteristics for two-dimensional multi-conductor in liquid crystal displays
Authors: Lin Kun-Wei , Shieh Han-Ping D. , Su Feng-Cheng D.
Published: July 2002

The capacitance voltage characteristics for the two-dimensional multi-conductor in liquid crystal displays (LCDs) are numerically derived by the method of successive over relaxation (SOR). The nonlinear and anisotropic properties of dielectric constant in the LC cell depend on the orientation of LC molecules under the influence of inhomogeneous electric field. An LC continuum theory implemented by tensor takes elastic anisotropy and inhomogeneous electric field into consideration to calculate the two-dimensional molecule orientations and potential distribution in LCDs. The dependence of capacitance on applied voltages and the geometric of LC cell is quantitatively described. Nonlinear capacitance results in capacitive coupling which causes flicker and adversely degrades image retention in LCD.
In-plane-gate transistors on nonepitaxial silicon directly written by focused-ion-beam implantation
Authors: Crell C. , Wieczorek K. , Schreiber H.-U. , Wieck A. D.
Published: July 2002

It is demonstrated that focused-ion-beam written in-plane-gate transistors, working at room temperature can be realized on (100) silicon-on-insulator wafers, separated by implanted oxygen, without the need for epitaxial growth processes. Typical channel widths are in the sub-μm range. Their electrical features at room temperature are characterized by transport and Hall measurements. The channel current is measured as a function of the geometrical channel width and the implanted dose. Activation of the implanted gallium by rapid thermal annealing changes the character of the insulating lines from Ohmic barriers to npn-junctions. Consequently the leakage current across the barriers decreases significantly, the direct current output characteristics of the transistors are improved with higher implantation doses and smaller geometrical channel widths are achievable.
Enhancement of titanium nitride barrier metal properties by nitrogen radical assisted metalorganic chemical vapor deposition
Authors: Chang Y. H. , Chun J. S. , Oh J. E. , Won S. J. , Paek S. H. , Lee H. D. , Lee S. I. , Choi J. S. , Lee J. G.
Published: July 2002

Using metalorganic chemical vapor deposition assisted by a nitrogen radical irradiation generated by rf plasma, we have enhanced the quality and the step coverage of titanium nitride barrier metals for the contact holes with a high aspect ratio and a submicron radius. Electrical resistivity measurements show that the film resistivity improves by a factor of five as the proper nitrogen irradiation has been applied. The step coverage in a contact hole with 0.4 μm diam and 3:1 aspect ratio has been improved from 50% to 80% by applying nitrogen plasma, clearly demonstrating the effectiveness of this technique in the conformal deposition of barrier metals for the ultra-large scale integration. The incident nitrogen radical is believed to play several roles, such as the enhancement of surface migration rate of molecules and the reduction of the amount of hydrocarbon incorporating into the film during the deposition.
Shock-induced polarization in normal-hexane
Authors: Saxena Kanchan , Hironaka Yoichiro , Hirai Hisako , Kondo Ken-ichi
Published: July 2002

The shock-induced electromotive force has been observed in normal-hexane as dielectric in a short circuited capacitor in the pressure range between 2.47 and 6.22 GPa. The induced current is inversely proportional to the initial thickness of the dielectric and is in accordance with Allison’s theory to some extent. The magnitude of polarization is of the order of 10−6–10−5 C/m2 and proportional to particle velocity in the pressure range studied.
Microstructure, friction, and wear characteristics of the as-deposited and carbon ion-implanted diamond films
Authors: Wu Richard L. C. , Rai A. K. , Miyoshi Kazuhisa
Published: July 2002

The microstructure, friction and wear characteristics of the as-deposited and carbon ion (160 keV, 6.7×1017 ions/cm2) implanted polycrystalline diamond films grown by plasma-enhanced chemical vapor deposition were studied. Cross sectional transmission electron microscopy revealed the amorphous nature of the ion bombarded film. Raman peaks of the ion-implanted film are found to be consistent with the noncrystalline carbon. The pin-on-disk technique was used to determine the friction and wear characteristics of the diamond films in an ultrahigh vacuum (10−7 Pa) at room temperature. Compared to the as-deposited film, considerable reduction in friction and wear of the ion-implanted film was observed.
On the fabrication of annealed proton exchanged waveguides with electric field poled domain reversals in Z-cut LiNbO3
Authors: Li W. H. , Tavlykaev R. , Ramaswamy R. V. , Samson S.
Published: July 2002

The influence of annealed proton exchanged (APE) waveguides on domain inversion in Z-cut LiNbO3 is reported. For this study, pyrophosphoric acid is used to fabricate planar APE waveguides, both before and after creating domain inversion through the application of an external electric field at room temperature. Domain inversion produced in this manner is shown to sustain the APE process. However, domain inversion is not producible in portions of the substrates having APE waveguides on both crystal faces. The implication of this result for integrated optic device fabrication is discussed.
In situ scanning tunneling microscopy of GaAs(001), (111)A, and (111)B surfaces in sulfuric acid solution
Authors: Yao Hideki , Yau Shueh-Lin , Itaya Kingo
Published: July 2002

In situ electrochemical scanning tunneling microscopy (STM) was used to examine n-type GaAs(001), (111)A, and (111)B surfaces in 0.05 M sulfuric acid. Cathodic polarization of the GaAs electrodes effectively inhibited the oxidation of the surface, making it possible to acquire STM images with atomic resolution. Atomically-flat terrace-step structures were consistently observed on all surfaces prepared by the chemical etching method. Steps observed on these surfaces are composed of double layers with step heights of 0.28 and 0.33 nm for the (001) and (111) surfaces, respectively. In situ STM atomic images revealed that those surfaces have (1×1) structures with the square and hexagonal lattices, respectively.