A 5-GByte/s data-transfer scheme with bit-to-bit skew control forsynchronous DRAM

This paper describes a 5-GByte/s data-transfer scheme suitable for synchronous DRAM memory. To achieve a higher data-transfer frequency, the properties were improved based on the frequency analysis of the memory system. Then, a bit-to-bit skew compensation technique that eliminates incongruent skew between the signals is described with a new, multioutput controlled delay circuit to accomplish bit-to-bit skew compensation by controlling transmission timing of every data bit. Simulated maximum data-transfer rate of the proposed memory system resulted in 5.1/5.8 GByte/s (321/365 MHz, ×64 bit, double data rate) for data write/read operation, respectively     

Structural advantages of rectangular-like channel cross-section on electrical characteristics of silicon nanowire field-effect transistors

We have experimentally demonstrated structural advantages due to rounded corners of rectangular-like cross-section of silicon nanowire (SiNW) field-effect transistors (FETs) on on-current (I_ON), inversion charge density normalized by a peripheral length of channel cross-section (Q_inv) and effective carrier mobility (μ_eff). The I_ON was evaluated at the overdrive voltage (V_OV) of 1.0 V, which is the difference between gate voltage (V_g) and the threshold voltage (V_th), and at the drain voltage of 1.0 V. The SiNW nFETs have revealed high I_ON of 1600 μA/μm of the channel width (w_NW) of 19 nm and height (h_NW) of 12 nm with the gate length (L_g) of 65 nm. We have separated the amount of on-current per wire at V_OV = 1.0 V to a corner component and a flat surface component, and the contribution of the corners was nearly 60% of the total I_ON of the SiNW nFET with L_g of 65 nm. Higher Q_inv at V_OV = 1.0 V evaluated by advanced split-CV method was obtained with narrower SiNW FET, and it has been revealed the amount of inversion charge near corners occupied 50% of all the amount of inversion charge of the SiNW FET (w_NW = 19 nm and h_NW = 12 nm). We also obtained high μ_eff of the SiNW FETs compared with that of SOI planar nFETs. The μ_eff at the corners of SiNW FET has been calculated with the separated amount of inversion charge and drain conductance. Higher μ_eff around corners is obtained than the original μ_eff of the SiNW nFETs. The higher μ_eff and the large fractions of I_ON and Q_inv around the corners indicate that the rounded corners of rectangular-like cross-sections play important roles on the enhancement of the electrical performance of the SiNW nFETs.     

Programmed High‐Hole‐Mobility Supramolecular Polymers from Disk‐Shaped Molecules

In this paper a simple, casting solution technique for the preparation of two‐dimensional (2D) arrays of very‐high molecular weight (MW) 1D‐Pc supramolecular inorganic polymers is described. The soluble fluoroaluminium tetra‐tert‐butylphthalocyanine (ttbPcAlF) is synthesized and characterized, which can be self‐assembled to form 2D arrays of very‐high‐MW 1D‐Pc supramolecular inorganic polymers. High‐resolution transmission electron microscopy (HRTEM) demonstrates that the 1D‐ttbPcAlF, having a cofacial ring spacing of ～0.36 nm and an interchain distance of ～1.7 nm, self‐assembles into 2D‐nanosheets (～140 nm in length, ～20 nm in width, and equivalent to MW of 3.2 × 10⁵ g mol^?1). The film cast from a 1,2‐dichloroethane (DCE) solution shows a minimum hole‐mobility of ～0.3 cm² V^?1 s^?1 at room temperature by flash‐photolysis time‐resolved microwave conductivity (TRMC) measurements and a fairly high dark dc‐conductivity of ～1 × 10^?3 S cm^?1.     

All-optical discrimination based on nonlinear transmittance of MQWsemiconductor optical gates

This paper proposes an all-optical regenerator utilizing a novel all-optical discriminator. The impacts of nonlinearity of optical gates on discrimination performance are estimated. The evaluation of discrimination performance shows that amplified spontaneous emission noise and wave form distortion in optical signals can be effectively suppressed. We experimentally demonstrate the suppression using a low-temperature-grown optical switch up to 10 Gb/s     

Characteristics of transients among periodic attractors controlledby high-frequency injection in a chaotic laser diode

We numerically studied statistics of the transient response time when switching between periodic attractors obtained through chaos control with a high-frequency injection method in a laser diode that is subject to optical feedback. Each transient response time significantly depends on its position in the starting attractor, whereas the statistical distributions of the response times for many transients are determined almost entirely by the final attractor. The average transient response time is 40 times larger than the round time in the controlled periodic attractors. The transient response time is also strongly affected by the external cavity length. The shortest average transient response time is obtained at a minimum external cavity length and a zero phase difference between the laser field and the feedback light field     

An improved design method of Rotman lens antennas

A Rotman lens is used to feed a linear array antenna for wideband use. A relationship between design parameters for realizing a Rotman lens has been derived by introducing a new design variable. The design method which minimizes the phase error on the aperture of the linear array antenna has been shown. For large array length, the above phase error due to this method becomes considerably smaller than that due to a conventional method. This improved method makes it possible to design small and low-loss Rotman lens antennas.     

Critical thickness of GaAs/InGaAs and AlGaAs/GaAsP strained quantum wells grown by organometallic chemical vapor deposition

In this paper we describe a study of strained quantum wells (QWs) as a means to experimentally observe the critical thickness (h _c) for the formation of interfacial misfit dislocations. Two material systems were investigated: GaAs/In_0.11Ga_0.89As, in which the QW layers are under biaxialcompression, and Al_0.35Ga_0.65As/GaAs_0.82P_0.18, in which the QW layers are under biaxialtension. Samples were grown by atmospheric pressure organometallic chemical vapor deposition, and characterized by low-temperature photoluminescence (PL), x-ray diffraction, optical microscopy, and Hall measurements. For both material systems, the observed onset of dislocation formation agrees well with the force-balance model assuming a double-kink mechanism. However, overall results indicate that the relaxation is inhomogeneous. Annealing at 800–850° C had no significant effect on the PL spectra, signifying that even layers that have exceededh _c and have undergone partial relaxation are thermodynamically stable against further dislocation propagation.     

Two-dimensional theory of distributed feedback semiconductor lasers

A theory which takes account of the two dimensional waveguide structure of the distributed-feedback (DFB) laser is presented. Laser threshold conditions in the case of no external reflections are calculated for a three-layer model in which one cladding layer has a periodically changing dielectric constant. In contrast with the coupled-wave theory the threshold conditions are found to be asymmetric with respect to the Bragg frequency. The longitudinal mode which lies below and nearest the Bragg frequency has the lowest threshold gain. The difference between the threshold gains of the two adjacent longitudinal modes straddling the Bragg frequency has a maximum as a function of the coupled strength of the grating     

Experimental and numerical analysis of channel-length-dependent electrical properties in bottom-gate,bottom-contact organic thin-film transistors with Schottky contact

Channel length dependence of field-effect mobility and source/drain parasitic resistance in pentacene thin-film transistors with a bottom-gate, bottom-contact configuration was investigated. Schottky barrier effect such as nonlinear behaviors in transistor output characteristics appeared and became more prominent for shorter channel length less than 10 μm, raising some concerns for a simple utilization of conventional parameter extraction methods. Therefore the gate-voltage-dependent hole mobility and the source/drain parasitic resistance in the pentacene transistors were evaluated with the aid of device simulation accounting for Schottky contact with a thermionic field emission model. The hole mobility in the channel region shows smaller values with shorter channel length even after removing the influence of Schottky barrier, suggesting that some disordered semiconductor layers with low carrier mobility exist near the contact electrode. This experimental data analysis with the simulation enables us to discuss and understand in detail the operation mechanism of bottom-gate, bottom-contact transistors by considering properly each process of charge carrier injection, carrier flow near the contact region, and actual channel transport.     

A real-time digital VCR encode/decode and MPEG-2 decode LSIimplemented on a dual-issue RISC processor

A real-time system large-scale-integrated circuit (LSI) for digital video cassette recorder (DVCR) encoding/decoding and MPEG-2 decoding is implemented on a dual-issue RISC processor (DRISC) with dedicated hardware optimized for video-block processing. The DRISC achieves 972-MOPS software performance and can execute fixed-length data processing at the block level as well as processing at the macro-block level and above for the DVCR/MPEG-2. The dedicated hardware for variable-length coding/decoding can encode and decode codes for both the DVCR and the MPEG-2 by changing translation tables. The dedicated hardware for video-block loading can process video-block data transfers with half-pel operations. The LSI size is 7.7×7.2 mm² in a 0.25-μm CMOS process