Thermal stability of interfaces between metals and InP-based materials

The thermal stability of interfaces between metals (Ni, Pt, Ti, Mo) and III-V compound semiconductors has been investigated by the application of Rutherford backscattering spectrometry. Metal diffusion and interfacial lattice disorder of the semiconductors were analyzed for various metal/semiconductor samples annealed at temperatures up to 500°C. The interfaces of Ni/GaAs and Ti/GaAs were found to be more stable than those of Ni/In-based semiconductors and Ti/ In-based semiconductors, respectively. Faster diffusion of Pt atoms was ob-served in In-and As-containing materials than in P-containing materials. Mo/ semiconductor interfaces were the most stable.     

A transceiver PIC for bidirectional optical communication fabricated by bandgap energy controlled selective MOVPE

A transceiver PIC consisting of a DFB-LD, a receiver PD and a Y-shaped branch waveguides is realized by in-plane bandgap energy controlled selective MOVPE. Both active and passive core layers are formed in one step selective growth, and complicated fabrication procedure is no longer required. More than 1 mW fiber coupled power and 7 GHz receiver bandwidth are obtained. The modulation and detection operations at 500 Mb/s are successfully demonstrated.     

1.5 nm direct-tunneling gate oxide Si MOSFET's

In this paper, normal operation of a MOSFET with an ultra-thin direct-tunneling gate oxide is reported for the first time. These high current drive n-MOSFET's were fabricated with a 1.5 nm direct-tunneling gate oxide. They operate well at gate lengths of around 0.1 μm, because the gate leakage current falls in proportional to the gate length, while the drain current increases in inverse proportion. A current drive of more than 1.0 mA/μm and a transconductance of more than 1,000 mS/mm were obtained at a gate length of 0.09 μm at room temperature. These are the highest values ever obtained with Si MOSFET's at room temperature. Further, hot-carrier reliability is shown to improve as the thickness of the gate oxide is reduced, even in the 1.5 nm case. This work clarifies that excellent performance-a transconductance of over 1,000 mS/mm at room temperature-can be obtained with Si MOSFET's if a high-capacitance gate insulator is used     

A rod matrix compensator for small-field intensity modulated radiation therapy: a preliminary phantom study

A compensator made of a tungsten-based rod matrix has been proposed for small-field intensity modulated radiation therapy. The compensator was attached to a 6 MV linac gantry head. The proposed compensator could modulate the X-ray intensity with a step of 10% and a minimum transmission of 2.5%.     

Self‐consistent electrical parameter extraction from bias dependent spectral response measurements of III‐V multi‐junction solar cells

Spectral response of multi‐junction solar cell is complicated because of the interplay between external measurement conditions such as bias light intensity, monochromatic light intensity, bias voltage, and intrinsic electrical properties of series interconnected subcells. In this paper, we report an experimental study on the bias voltage‐dependent spectral response (SR) for multi‐junction solar cell. A self‐consistent iteration loop was developed from a nonlinear least square Powell hybrid algorithm that was used for curve fitting the experimental SR versus bias voltage data of each subcell. We demonstrated for the first time that this approach enabled us to derive the electrical parameters such as dark saturation currents (J₀), shunt resistance (R_sh), series resistance (R_s), and spectra response (J_photo) for each subcell of a Ga_0.99In_0.01As/Ge dual junction solar cell with stable convergence. The accuracies of the fitting results were confirmed by the agreement between the J–V curves calculated on the basis of these parameters and the experimental J–V curve of multi‐junction solar cell measured under AM1.5 and 1 sun condition. Copyright © 2013 John Wiley & Sons, Ltd.     

Rocket-triggered lightning experiments on zinc oxide arresters and their applications to power transmission lines

In measurements of rocket-triggered lightning current and voltage performed between 1986 and 1995 on the mountain top of Okushishiku in the Kanazawa area, the authors succeeded in artificially inducing winter lightning to arresters. Using the data obtained from those measurements, we analyzed the energy absorption characteristics of surge arresters, such as are installed on every transmission line tower for three phrases, by EMTP. The energy withstand capability of an individual arrester was verified to be approximately the same as the expected value. The analysis results for the energy share of each arrester connected in parallel showed that the usual light duty arresters installed on every tower have the possibility to be able to absorb extreme winter lightning energy even if the lightning hits the power line directly. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 25–33, 1998     

Efficient use of frequencies in terrestrial ISDB system

Requirements for a terrestrial ISDB system and the schemes for efficiently using frequencies to fulfil the requirements are discussed. One requirement of a terrestrial ISDB system is the efficient allocation of frequencies using a SFN (single frequency network). The SFN incorporates the great advantages of OFDM, which has excellent performance under multi-path conditions. The transmission characteristics of 64QAM-OFDM and the SFN capability using 64QAM-OFDM in the Kanto area, including the Tokyo metropolitan area, are analyzed. The results show that more than a 97% coverage ratio can be obtained even by using a single channel while the same area is covered currently by more than 30 analog channels. The other requirement is a scheme for efficiently using the available frequency band for various services. A transmission scheme concept called BST-OFDM (band segmented transmission-orthogonal frequency division multiplexing) is proposed as a transmission scheme for meeting the requirements of a terrestrial ISDB system. In the BST-OFDM scheme, data are transmitted in a number of OFDM blocks called a BST-segment, for which channel coding and modulation schemes can be independently defined to provide robustness in the transmission environment according to stationary, portable and mobile reception     

DX centers in AlxGa1-xAs bulk alloy,AlAs/GaAs ordered,and disordered superlattices

Properties of theDX centers in Al_0.5Ga_0.5As bulk alloy (b-AL), (AlAs)₂ (GaSa)₂ ordered superlattice (o-SL) and (AlAs) _m (GaAs) _n disordered superlattice (d-SL) (m = 1, 2, 3,n = 1, 2, 3) with the same macroscopic composition were measured and compared. By deconvolution of deep level transient spectroscopy (DLTS) spectrum due to theDX center, we have found a decrease in the number of separate peaks in DLTS spectrum in an intentionally atomic ordered arrangement. Visiting Scholar of the Japan Society for the Promotion of Science. On leave from Department of Electrical Engineering, San Jose State University, San Jose, California 95192-0084, USA.     

Oscillation spectra in He-Zn II and He-Cd II hollow cathode metal vapor lasers

This paper reports the measurement for the oscillation spectra in He-Zn II lasers at the 492.4 nm line and He-Cd II lasers at the 533.7 and 537.8 nm lines of the hollow cathode (HC) type with natural zinc or cadmium. The oscillation width of these lasers, which amounts to more than 2000 MHz, is unexpectedly broad in comparison with the theoretical gain profile; and the isotope shifts of the spectra which are caused by any two isotopes whose mass numbers differ by unity (DeltaM = 1) can be estimated to be as much as 300-500 MHz to explain such a broadened oscillation width. The dominant reason for the large isotope shifts is not so much the mass effects as the volume effects. The behavior of the spectra at the axial mode competition is also measured. The extraordinary appearances of the mode competition can be attributed to the influence of the isotope shifts upon the oscillation spectra. Moreover, the axial mode separation at the beginning of the mode competition is nearly coincident with the decay rate of the upper laser level.