Telcordia Technologies

About: Telcordia Technologies is a based out in . It is known for research contribution in the topics: Network packet & Node (networking). The organization has 3097 authors who have published 4737 publications receiving 237882 citations.

Enhancement-mode high electron mobility transistors (E-HEMTs) lattice-matched to InP

Abstract: The fabrication and characterization of high-speed enhancement-mode InAlAs/InGaAs/InP high electron mobility transistors (E-HEMTs) have been performed. The E-HEMT devices were made using a buried-Pt gate technology. Following a Pt/Ti/Pt/Au gate metal deposition, the devices were annealed in a nitrogen ambient, causing the bottom Pt layer to sink toward the channel. This penetration results in a positive shift in threshold voltage. The dc and RF performance of the devices has been investigated before and after the gate annealing process. In addition, the effect of the Pt penetration was investigated by fabricating two sets of devices, one with 25 nm of Pt as the bottom layer and the other with a 5.0 nm bottom Pt layer. E-HEMTs were fabricated with gate lengths ranging from 0.3 to 1.0 /spl mu/m. A maximum extrinsic transconductance (g/sub mext/) of 701 mS/mm and a threshold voltage (V/sub T/) of 167 mV was measured for 0.3 /spl mu/m gate length E-HEMTs. In addition, these same devices demonstrated excellent subthreshold characteristics as well as large off-state breakdown voltages of 12.5 V. A unity current-gain cutoff frequency (f/sub t/) of 116 GHz was measured as well as a maximum frequency of oscillation (f/sub max/) of 229 GHz for 0.3 /spl mu/m gate-length E-HEMTs.

NOMAD: traffic-based network monitoring framework for anomaly detection

Abstract: Network performance monitoring is essential for managing a network efficiently and for ensuring reliable operation of the network. In this paper we introduce a scalable network monitoring framework, (NOMAD), that detects network anomalies through the characterization of the dynamic statistical properties of network traffic. NOMAD relies on high resolution measurements and on-line analysis of network traffic to provide real-time alarms in the incipient phase of network anomalies. It incorporates a suite of anomaly identification algorithms based on path changes, flow shift, and packet delay variance, and relies extensively on IP packet header information, such as TTL, source/destination address and packet length, and router's timestamps. NOMAD can be deployed in a single backbone router or incrementally in a regional or large scale network for detecting and locating network anomalies by correlating spatial and temporal network state information.

An investigation of a nonspiking Ohmic contact to n-GaAs using the Si/Pd system

Abstract: A low-resistance nonspiking Ohmic contact to n-GaAs is formed via solid-state reactions utilizing the Si/Pd/GaAs system. Samples with Si to Pd atomic ratios greater than 0.65 result in specific contact resistivity of the order of 10 −6 Ω cm 2 , whereas samples with atomic ratios less than 0.65 yield higher specific contact resistivities or rectifying contacts. Rutherford backscattering spectrometry, cross-sectional transmission electron microscopy, and electron diffraction patterns show that a Pd, Si layer is in contact with GaAs with excess Si on the surface after the Ohmic formation annealing. This observation contrasts with that on a previously studied Ge/Pd/GaAs contact where Ohmic behavior is detected after transport of Ge through PdGe to the interface with GaAs. Comparing the Ge/Pd/GaAs system with the present Si/Pd/GaAs system suggests that a low barrier heterojunction between Ge and GaAs is not the primary reason for Ohmic contact behavior. Low-temperature measurements suggest that Ohmic behavior results from tunneling current transport mechanisms. A regrowth mechanism involving the formation of an n + GaAs surface layer is proposed to explain the Ohmic contact formation.

A broadband optical multicast switch

Abstract: We propose a new optical muhicast switching system based on a two-phase contention resolution algorithm This architec ture may simultaneously support packet switching, and circuat channel emulation. It can handle time-multiplexed variable bit rate random access packets and reserved access packets in a single framework that incorporates unicast and multicast switching. We present the overall switch architecture, its optical device requirements, and possible implementation schemes. Performance enhancements through the addition of multiple tracks are discussed which indicate the flexibility inherent in this design. Results of an analysis of the throughput and switch performance are discussed.

Large critical current densities in YBa2Cu3O7−x thin films made at high deposition rates

Abstract: Critical current densities (Jc) in YBa2Cu3O7−x films made at deposition rates from 0.1 to 14.5 nm/s (∼50 μm/h) were measured using a direct transport method. As the deposition rate was increased by two orders of magnitude, the films exhibited no marked degradation in current carrying capability with Jc of ∼4×106 A/cm2 at 77 K and zero field. Jc for all the films showed similar behavior under a magnetic field up to 8 T, although extra structural defects were found in the films deposited at the higher rates. The results from this experiment indicate the feasibility for coating wires, tapes, and other macroscopic shapes with high Tc superconductors using proper vapor deposition techniques.