Development of new semiconductors with high carrier mobility is strongly needed to realize future system-in-displays. To achieve this, we have been investigating low-temperature crystallization of a-Si1-xGex (0≤x≤1) on insulating films. Present paper focuses our recent progress of the Ni-induced lateral crystallization of a-Si1-xGex (0≤x≤1). Effects of the Ge fraction and the electric field on the growth characteristics are discussed.
The improvement of current drivability and short channel effect is very important for ultrasmall MOS devices technology. SiGe-channel pMOSFETs are one of the most promising devices because hole mobility in the SiGe layers is enhanced. In the previous work, it has been reported that Super self-aligned shallow junction electrode (S3E) MOSFETs formed by selective B-doped SiGe CVD are effective for the suppression of short channel effect. In this paper, it is clarified that the (S3E) pMOSFETs with Si0.65Ge0.35-channel are realized not only with suppression of punch through due to the ultrashallow B-diffused source/drain but also with enhancement of maximum linear transconductance due to the low parasitic resistance, compared to that with the Si-channel fabricated by the same process conditions.
We have grown thin strain-relaxed SiGe buffer layers on silicon-on-insulator (SOI) substrates with pure-edge dislocation network at the SiGe/SOI interface. Dislocation morphology and crystalline mosaicity of the SiGe layers have been analyzed by X-ray diffraction two-dimensional reciprocal space mapping and transmission electron microscopy. It was found that dislocation propagation at the SiGe/SOI interface and resultant crystalline mosaicity of the SiGe layer are critically dependent on the thickness of SOI layer. Image force exerted on the dislocations accounts for this SOI thickness dependence.
We have proposed a strain-relaxed quadruple-layer buffer on the basis of our previously proposed thin double- and triple-layer formation mechanisms. With the quadruple-layer buffer, we have demonstrated that misfit dislocations are mainly generated and distributed in the two lower interfaces and the third and fourth layers drive the dislocation generation and prevent the dislocations from propagating to the surface. A resonant tunneling diode fabricated with the quadruple-layer buffer exhibits both a high current density and a high peak-to-valley current ratio.
For the next generation wireless terminals used in the software defined radio (SDR), multi-band / multi-mode transceivers and their MMIC are required which cover the wide RF frequency range from several hundreds MHz up to several GHz. In this paper, 0.8-5.2GHz broad-band SiGe-MMIC quadrature mixer (Q-MIX) for multi-band / multi-mode direct conversion receiver has been developed. By using a static type frequency divider as a 90 degrees local (LO) power divider, measured error vector magnitude (EVM) of less than 3.1% can be achieved in the cases of 0.8/2.1GHz W-CDMA and 5.2GHz wireless Local Area Network (LAN) (IEEE 802.11a) reception. This Q-MIX also shows broad-band characteristic for base-band signal and is applicable for 4G cellular. By using fabricated Q-MIX, a multi-band / multi-mode (1.9GHz (3rd generation cellular (W-CDMA)) / 5.2GHz (4th generation cellular (Multi-Carrier (MC)-CDMA))) receiver has been developed and it has firstly demonstrated the successful reception of motion picture via W-CDMA and MC-CDMA.
It is reported for the first time that hot-carrier-induced degradation occurs in a SiGe/Si heterostructure introduced into the channel region of SiGe/Si-hetero-MOSFETs, using a newly established elaborate low-temperature charge pumping (LTCP) technique. Moreover, the hetero-interface trap density generated and the width of the degraded region are estimated from the LTCP characteristics. These results will enable new levels of improvement to the performance and reliability of strained-Si and SiGe devices.
We fabricated an organic light-emitting field effect transistors (OLEFET) using a co-deposited layer of TPTPT and NTCDA which has p-type and n-type semiconducting behaviors, respectively. The organic layer was formed on a comb type electrode (source-drain electrodes) with a channel length of 25μm on a p-Si/SiO2 substrate. Bipolar and EL characteristics were investigated by changing co-deposition ratio of TPTPT and NTCDA. In the optimum deposition ratio, we observed typical ambipolar characteristics, demonstrating saturation current characteristics at low Vd (source-drain voltage), followed by divergent current characteristics at high Vd.
In this paper we propose a new positioning control method for the compact linear motor developed for EMV(ElectroMagnetic engine Valve). This motor has a nonlinear property due to the detent force and the friction. We design a positioning controller using sliding mode servo control with variable switching hyperplane in order to realize the robust property against the nonlinear property and the high speed positioning. The effectiveness of the proposed controller is confirmed by some experiments.
We have proposed and examined one-by-one (O-O) and point-to-point (P2P) link integration scheme over native-Ethernet optical ring networks for scalable customer-owned metropolican area network application (CO-MAN). The 2-link integration enables us to construct economical networks, which was clarified by smaller number of optical transceivers required to provide IP services. The experiments clarified that the integration of the O-O and P2P links was successfully made through 35 km long fiber ring. The failure restoraion function was also confirmed to work properly, when the service ring failure occurred. All the packet transmissions were made on the native-Ethernet base, which allows the network administrators of the CO-MAN to manage the network in the same way as in the commonly-used LANs.
Emerging broadband networks and high performance of PCs provide new business opportunities of the live video streaming services for the Internet users in sport events or in music concerts. Digital watermarking for video helps to protect the copyright of the video content and the real-time processing is an essential requirement. For the small start of new business, it should be achieved by flexible software without special equipments. This paper describes a novel real-time watermarking system implemented on a commodity PC. We propose the system architecture and methods to shorten watermarking time by reusing the estimated watermark imperceptibility among neighboring frames. A prototype system enables real time processing in a series of capturing NTSC signals, watermarking the video, encoding it to MPEG4 in QGVA, 1Mbps, 30fps style and storing the video for 12 hours in maximum
The problem of iterative learning control is considered for a class of linear discrete systems with multiple time delays. In this paper, it is assumed that the initial condition for discrete time-delay systems is unknown at each iteration. For such a class of discrete time-delay systems, a method is presented whereby a class of discrete iterative learning control schemes can be constructed. It is shown that under some given conditions, the constructed iterative learning controllers can guarantee the asymptotic convergence of the output error between the given desired output and the actual output through the iterative learning process. Finally, a numerical example is given to demonstrate the validity of the results.
An interactor plays a basic role in the design problem of multivariable control systems, e.g., the model matching control, decoupling control, adaptive control, disturbance decoupling control, and etc. For example, it is well known that the linear multivariable system is decouplable by the static state feedback if and only if it has a diagonal interactor. But, in general, the interactor is a lower left triangular matrix, which makes the design problem of multivariable control systems complicated. From this point of view, the precompensator so that the total system has a diagonal interactor is important for multivariable control system to simplify its design procedure. This paper concerns the systematic design method of the precompensator for a diagonal interactor using Markov parameters of the plant. It will be also proved that this compensator is always obtained by proposed design algorithm. Furthermore, this argument will be a basic idea when this technique is apply to the non-linear multivariable system.
In this paper a new state observer is proposed to estimate the minimum phase state contained in objects with long delay time. The minimum phase state of the object can be controlled with two degree of freedom which have the stable closed-loop and the input-output response designed. The combination of the minimum phase state observer and the two degree of freedom controller can accomplish both the regulated disturbance and the relatively high speed input-output response. Simulations of numerical examples are shown in comparison to the modified Smith predictor.
In this paper, a linear system with multiple and mutually independent time-varying delays in the state is considered as a plant, and a method to construct a memoryless feedback law is proposed. The feedback gain is constant and is calculated via a solution of linear matrix inequalities containing the upper bounds of all derivative delays. It is shown that the resulting closed loop system is asymptotically stable and the feedback control minimizes some quadratic cost functional, so that it belongs to a class of linear quadratic regulators. It is a remarkable feature that the weighting matrix in the cost functional is time-varying. In spite of this feature, it is shown that the regulator has some robust stability against a class of static nonlinear or a class of dynamic linear perturbations in the input channel as well as the ordinary LQ regulator. The design procedure is demonstrated and the robust stability of the closed loop system is examined with a numerical example.
Our brain has three different learning paradigms: supervised, unsupervised and reinforcement learning. And it is suggested that those learning paradigms relate deeply to the cerebellum, cerebral cortex and basal ganglia in the brain, respectively. Inspired by these knowledge of brain, we present a brain-like learning system with those three different learning algorithms. The proposed system consists of three parts: the supervised learning (SL) part, the unsupervised learning (UL) part and the reinforcement learning (RL) part. The SL part, corresponding to the cerebellum of brain, learns an input-output mapping by supervised learning. The UL part, corresponding to the cerebral cortex of brain, is a competitive learning network, and divides an input space to subspaces by unsupervised learning. The RL part, corresponding to the basal ganglia of brain, optimizes the model performance by reinforcement learning. Numerical simulations show that the proposed brain-like learning system optimizes its performance automatically and has superior performance to an ordinary neural network.
N-gram indexing method is the most popular algorithm for the Japanese full text search system where each index consists of serial N characters. Especially the full text search for Japanese text usually has the 2-gram characters index as base in order to save the volumes of the index file. Although the additional higher-gram index is expected to improve the performance for searching indices, we have no experimental evaluation with additional higher-gram indices. This paper presents the evaluation about improving the text search performance with additional higher-gram indices by Search Term Intensive Approach which decides the term for higher-gram indices depend upon the appearance ratio in application programs as the searching term. On the concrete evaluation, the number of paper articles for searching is one or two hundred thousands, and the simulation for 5 or more gram additional indices can be applied add to evaluation for 3,4-gram additional indices.
Private finance initiative is a business scheme that materializes social infrastructure and public services by utilizing private-sector resources. In this paper we propose a new method to optimize capital structure, which is the ratio of capital to debt, and senior-sub structure, which is the ratio of senior loan to subordinated loan, for private finance initiative. We make the quantitative analysis of a private finance initiative's project using the proposed method. We analyze trade-off structure between risk and return in the project, and optimize capital structure and senior-sub structure. The method we propose helps to improve financial stability of the project, and to make a fund raising plan that is expected to be reasonable for project sponsor and moneylender.