Consequences of structural disorder on laser properties in quantumwire lasers

The effect of interface-roughness-related disorder on the electronic and optoelectronic properties of a quantum wire structure are studied. It is seen that the disorder causes strong localization in the quasi-one-dimensional system. While the electronic states are seriously perturbed, the density of states is not affected drastically. Optoelectronic properties as reflected in the interband transition related phenomenon are not found to suffer significant deterioration as a result of the disorder. However, the results suggest that intraband relaxation processes may be seriously affected because of electron (hole) states being localized in different regions of the wire     

Colloidal processing of polymer ceramic nanocomposite integral capacitors

Polymer ceramic composites form a suitable material system for low temperature fabrication of embedded capacitors appropriate for the MCM-L technology. Improved electrical properties such as permittivity can be achieved by efficient filling of polymers with high dielectric constant ceramic powders such as lead magnesium niobate-lead titanate (PMN-PT) and barium titanate (BT). Photodefinable epoxies as the matrix polymer allow fine feature definition of the capacitor elements by conventional lithography techniques. The optimum weight percent of dispersant is tuned by monitoring the viscosity of the suspension. The dispersion mechanism (steric and electrostatic contribution) in a slightly polar solvent such as propylene glycol methyl ether acetate (PGMEA) is investigated from electrophoretic measurements. A high positive zeta potential is observed in the suspension, which suggests a strong contribution of electrostatic stabilization. By optimizing the particle packing using a bimodal distribution and modified processing methodology, a dielectric constant greater than 135 was achieved in PMN-PT/epoxy system. Suspensions are made with the lowest PGMEA content to ensure the efficiency of the dispersion and efficient particle packing in the dried film. Improved colloidal processing of nanoparticle-filled epoxy is a promising method to obtain ultra-thin capacitor films (<2/spl mu/m) with high capacitance density and improved yield. Capacitance of 35 nF/cm/sup 2/ was achieved with the thinnest films (2.5-3.0 /spl mu/m).     

CMOS implementation of a multiple-valued logic signed-digit fulladder based on negative-differentiaI-resistance devices

This paper presents a fully integrated implementation of a multivalued-logic signed-digit full adder (SDFA) circuit using a standard 0.6-μm CMOS process. The radix-2 SDFA circuit, based on two-peak negative-differentiaI-resistance (NDR) devices, has been implemented using MOS-NDR, a new prototyping technique for circuits that combine MOS transistors and NDR devices. In MOS-NDR, the folded current-voltage characteristics of NDR devices such as resonant-tunneling diodes (RTDs) are emulated using only nMOS transistors. The SDFA prototype has been fabricated and correct function has been verified. With an area of 123.75 by 38.7 μm² and a simulated propagation delay of 17 ns, the MOS-NDR prototype is more than 15 times smaller and slightly faster than the equivalent hybrid RTD-CMOS implementation     

Parameterized dataflow modeling for DSP systems

Dataflow has proven to be an attractive computation model for programming digital signal processing (DSP) applications. A restricted version of dataflow, termed synchronous dataflow (SDF), that offers strong compile-time predictability properties, but has limited expressive power, has been studied extensively in the DSP context. Many extensions to synchronous dataflow have been proposed to increase its expressivity while maintaining its compile-time predictability properties as much as possible. We proposed a parameterized dataflow framework that can be applied as a meta-modeling technique to significantly improve the expressive power of any dataflow model that possesses a well-defined concept of a graph iteration, Indeed, the parameterized dataflow framework is compatible with many of the existing dataflow models for DSP including SDF, cyclo-static dataflow, scalable synchronous dataflow, and Boolean dataflow. In this paper, we develop precise, formal semantics for parameterized synchronous dataflow (PSDF)-the application of our parameterized modeling framework to SDF-that allows data-dependent, dynamic DSP systems to be modeled in a natural and intuitive fashion. Through our development of PSDF, we demonstrate that desirable properties of a DSP modeling environment such as dynamic reconfigurability and design reuse emerge as inherent characteristics of our parameterized framework. An example of a speech compression application is used to illustrate the efficacy of the PSDF approach and its amenability to efficient software synthesis techniques. In addition, we illustrate the generality of our parameterized framework by discussing its application to cyclo-static dataflow, which is a popular alternative to the SDF model     

Analysis and characterization of photo-plethysmographic signal

Qualitative assessment of the overall clinical status of the subject and characterization of complex cardiovascular dynamics from digital blood volume pulsations measured noninvasively using a photo-plethysmographic device is addressed. A novel concept is employed to detect the dominant nonsinusoidal periodicity embedded in the data series and to extract the associated periodic component. The detection and the extraction of periodic component is performed with moving window to accommodate the variations of the physiological oscillations. The covariance matrix formed by the gradually varying pattern is used as a simple measure of qualitative assessment. Further, the characterization of the underlying system in the light of nonlinear dynamical analysis is also presented. The stable subjects are shown to behave as a low-dimensional system whereas the diseased subjects exhibit comparatively high dimensional activity.     

Effect of epitaxial realignment on the leakage behavior of arsenic-implanted,as-deposited polycrystalline Si-on-single crystal Si diodes

When dopants are indiffused from a heavily implanted polycrystalline silicon film deposited on a silicon substrate, high thermal budget annealing can cause the interfacial “native” oxide at the polycrystalline silicon-single crystal silicon interface to break up into oxide clusters, causing epitaxial realignment of the polycrystalline silicon layer with respect to the silicon substrate. Anomalous transient enhanced diffusion occurs during epitaxial realignment and this has adverse effects on the leakage characteristics of the shallow junctions formed in the silicon substrate using this technique. The degradation in the leakage current is mainly due to increased generation-recombination in the depletion region because of defect injection from the interface.     

Application of high-quality SiO/sub 2/ grown by multipolar ECR source to Si/SiGe MISFET

A 5 nm-thick SiO/sub 2/ gate was grown on an Si (p/sup +/)/Si/sub 0.8/Ge/sub 0.2/ modulation-doped heterostructure at 26 degrees C with an oxygen plasma generated by a multipolar electron cyclotron resonance source. The ultrathin oxide has breakdown field >12 MV/cm and fixed charge density approximately 3*10/sup 16/ cm/sup -2/. Leakage current as low as 1 mu A was obtained with the gate biased at 4 V. The MISFET with 0.25*25 mu m/sup 2/ gate shows maximum drain current of 41.6 mA/mm and peak transconductance of 21 mS/mm.<>     

An experimental study of 1.5 keV X-ray radiation effects on CMOS devices

The total dose radiation effects are studied on CMOS devices consisting of n- and p-MOSFETs and logic circuits. The devices on a test chip were designed in two micron, double metal, single polysilicon, p-well CMOS technology and fabricated through the Metal-Oxide Semiconductor Implementation System (MOSIS) foundry. Effects of 1.5 keV AlK_a X-ray irradiation on the threshold voltage of n- and p-MOSFETs, propagation delay time and voltage transfer characteristic of an inverter were observed and the results are presented. Degradation in performance of an inverter chain, a three stage ring oscillator and a four-by-four shift register was also observed with increasing radiation dose levels. The devices were unbiased during the irradiation. The samples were radiated at a dose rate of 1 × 10⁵ rads(SiO₂)/min.