Evanescent-Coupled Ge p-i-n Photodetectors on Si-Waveguide With SEG-Ge and Comparative Study of Lateral and Vertical p-i-n Configurations

Si-waveguide-integrated lateral Ge p-i-n photodetectors using novel Si/SiGe buffer and two-step Ge-process are demonstrated for the first time. Comparative analysis between lateral Ge p-i-n and vertical p-Si/i-Ge/n-Ge p-i-n is made. Light is evanescently coupled from Si waveguide to the overlaying Ge- detector, achieving high responsivity of 1.16 A/W at 1550 nm with f_{3 dB} bandwidth of 3.4 GHz for lateral Ge p-i-n detector at 5 V reverse bias. In contrast, vertical p-Si/i-Ge/n-Ge p-i-n has lower responsivity of 0.29 A/W but higher bandwidth of 5.5 GHz at -5 V bias. The higher responsivity of lateral p-i-n detectors is attributed to smaller optical mode overlap with highly doped Ge region as in vertical p-i-n configuration.     

Ge-Rich (70%) SiGe Nanowire MOSFET Fabricated Using Pattern-Dependent Ge-Condensation Technique

A top-down approach of forming SiGe-nanowire (SGNW) MOSFET, with Ge concentration modulated along the source/drain (Si_0.7Ge_0.3) to channel (Si_0.3Ge_0.7) regions, is presented. Fabricated by utilizing a pattern-size-dependent Ge-condensation technique, the SGNW heterostructure PMOS device exhibits 4.5times enhancement in the drive current and transconductance (G_m) as compared to the homojunction planar device (Si_0.7Ge_0.3). This large enhancement can be attributed to several factors including Omega-gated nanowire structure, enhanced hole injection efficiency (due to valence band offset), and improved hole mobility (due to compressive strain and Ge enrichment in the nanowire channel).     

Low-Cost and High-Speed SOI Waveguide-Based Silicide Schottky-Barrier MSM Photodetectors for Broadband Optical Communications

Silicon-on-insulator waveguide-based silicide Schottky-barrier metal-semiconductor-metal (MSM) photodetectors were fabricated using a simple low-temperature Si-process. Without optimization, the detector achieves a 3-dB bandwidth of ~ 7 GHz at -3-V bias and a responsivity of ~ 19 mA/W at -1-V bias, with very weak dependence on wavelength ranging from 1520 to 1620 nm. Compared to the silicide Schottky-barrier photodiode with the same NiSi₂ absorber, the MSM detectors offer the benefits of high speed, large responsivity, and ease of fabrication. Approaches for optimization are addressed.     

An information-lossless decomposition theory of relational information systems

Relational information systems, systems that can be represented by tables of finite states, are commonly used in many areas such as logic circuits, finite-state machines, and relational databases. Decomposition is a natural method of handling complex systems and removing redundancies. It splits a table into a network of smaller, simpler, and interrelated new tables. In order to preserve the original features of the system, any valid decomposition must be lossless. Commutative partitions play an important role in the decomposition. The commutative property is essentially a general algebraic formulation of independency of two partitions. We express the interdependency of two commutative partitions by a bipartite graph, and classify the hierarchical independency structures by the topological property of bipartite graphs. In particular, we show that two partitions are decomposable, the strongest version of dependency, if and only if the associate bipartite graph is uniform. We also adopt Shannon's entropy to quantify the amount of information contained in each partition, and formulate the information-lossless decomposition by the entropy conservation identity. Under the assumption of running intersection property, we show that the general formulation of information-lossless decomposition of relational systems is given by the entropy inclusion-exclusion equality. Applications of these formulations to Boolean logic circuits and relational databases are presented to manifest the information-lossless decomposition processes.     

High-performance fully depleted silicon nanowire (diameter /spl les/ 5 nm) gate-all-around CMOS devices

This paper demonstrates gate-all-around (GAA) n- and p-FETs on a silicon-on-insulator with /spl les/ 5-nm-diameter laterally formed Si nanowire channel. Alternating phase shift mask lithography and self-limiting oxidation techniques were utilized to form 140- to 1000-nm-long nanowires, followed by FET fabrication. The devices exhibit excellent electrostatic control, e.g., near ideal subthreshold slope (/spl sim/ 63 mV/dec), low drain-induced barrier lowering (/spl sim/ 10 mV/V), and with I/sub ON//I/sub OFF/ ratio of /spl sim/10/sup 6/. High drive currents of /spl sim/ 1.5 and /spl sim/1.0 mA//spl mu/m were achieved for 180-nm-long nand p-FETs, respectively. It is verified that the threshold voltage of GAA FETs is independent of substrate bias due to the complete electrostatic shielding of the channel body.     

$nhbox{-ZnO}/nhbox{-GaAs}$ Heterostructured White Light-Emitting Diode: Nanoscale Interface Analysis and Electroluminescence Studies

n-ZnO/n-GaAs heterostructured light-emitting diodes have been fabricated by a low-cost ultrasonic spray pyrolysis technique. Nanoscale interface analysis was carried out with scanning transmission electron microscopy. An ~ 8.6-nm-thick amorphous GaAsZnInO was found in the n -ZnO/n-GaAs interface. A strong and broad white electroluminescence band centered at ~ 525 nm and a weak near-infrared emission peaked at ~ 815 nm were observed when n-GaAs was positively biased. The 815-nm emission is believed to be related to the interface layer, and the 525-nm emission is assigned to the recombination of electrons from conduction band to deep-level holes in the ZnO layer.     

A multiple circular path convolution neural network system for detection of mammographic masses

A multiple circular path convolution neural network (MCPCNN) architecture specifically designed for the analysis of tumor and tumor-like structures has been constructed. We first divided each suspected tumor area into sectors and computed the defined mass features for each sector independently. These sector features were used on the input layer and were coordinated by convolution kernels of different sizes that propagated signals to the second layer in the neural network system. The convolution kernels were trained, as required, by presenting the training cases to the neural network. In this study, randomly selected mammograms were processed by a dual morphological enhancement technique. Radiodense areas were isolated and were delineated using a region growing algorithm. The boundary of each region of interest was then divided into 36 sectors using 36 equi-angular dividers radiated from the center of the region. A total of 144 Breast Imaging-Reporting and Data System-based features (i.e., four features per sector for 36 sectors) were computed as input values for the evaluation of this newly invented neural network system. The overall performance was 0.78-0.80 for the areas (Az) under the receiver operating characteristic curves using the conventional feed-forward neural network in the detection of mammographic masses. The performance was markedly improved with Az values ranging from 0.84 to 0.89 using the MCPCNN. This paper does not intend to claim the best mass detection system. Instead it reports a potentially better neural network structure for analyzing a set of the mass features defined by an investigator.     

Multicast-based inference of network-internal delay distributions

Packet delay greatly influences the overall performance of network applications. It is therefore important to identify causes and locations of delay performance degradation within a network. Existing techniques, largely based on end-to-end delay measurements of unicast traffic, are well suited to monitor and characterize the behavior of particular end-to-end paths. Within these approaches, however, it is not clear how to apportion the variable component of end-to-end delay as queueing delay at each link along a path. Moreover, there are issues of scalability for large networks. In this paper, we show how end-to-end measurements of multicast traffic can be used to infer the packet delay distribution and utilization on each link of a logical multicast tree. The idea, recently introduced in Caceres et al. (1999), is to exploit the inherent correlation between multicast observations to infer performance of paths between branch points in a tree spanning a multicast source and its receivers. The method does not depend on cooperation from intervening network elements; because of the bandwidth efficiency of multicast traffic, it is suitable for large-scale measurements of both end-to-end and internal network dynamics. We establish desirable statistical properties of the estimator, namely consistency and asymptotic normality. We evaluate the estimator through simulation and observe that it is robust with respect to moderate violations of the underlying model.     

Cryptanalysis of Hsiang‐Shih's authentication scheme for multi‐server architecture

From user point of view, password‐based remote user authentication technique is one of the most convenient and easy‐to‐use mechanisms to provide necessary security on system access. As the number of computer crimes in modern cyberspace has increased dramatically, the robustness of password‐based authentication schemes has been investigated by industries and organizations in recent years. In this paper, a well‐designed password‐based authentication protocol for multi‐server communication environment, introduced by Hsiang and Shih, is evaluated. Our security analysis indicates that their scheme is insecure against session key disclosure, server spoofing attack, and replay attack and behavior denial. Copyright © 2010 John Wiley & Sons, Ltd.     

Polarity dependence of charge to breakdown and interface state generation of oxynitride gate dielectrics prepared by rapid thermal processing

MOS devices were fabricated with dry thermal oxides, nitrided oxides and annealed nitrided oxides. The anneals were performed in O/sub 2/ or N/sub 2/ ambients using rapid thermal processing. Charge to breakdown, Q/sub bd/, and interface state generation, Delta D/sub it/, for these devices were studied using Fowler-Nordheim electron injection. The gate bias polarity dependence of Q/sub bd/ and Delta D/sub it/ was investigated. A model is proposed to explain the observed dependence of these quantities on the polarity of injection and process parameters.<>