Field effect semiconductor lasers

A new semiconductor laser, the field-effect semiconductor (FES) laser, in which the both sides of the active region are surrounded by the burying layers with the reverse-biased p-n junctions is proposed. The proposed FES laser is aQ-switching device based on the direct control of laser beam intensity by the internal loss modulation through the field effect. The structure design and the operating principles of the device are discussed. Numerical solution shows that a pulsewidth shorter than 30 ps can be obtained.     

Incorporation of Sb in GaAs1?xSbx (x<0.15) by molecular beam epitaxy

The composition of MBE-grown GaAs1?xSbx (x<0.15) is investigated as a function of growth temperature for constant As and Sb flux and as a function of Sb effusion cell temperature for a fixed growth temperature. Under conditions of constant As and Sb flux, x remains fairly constant for growth temperatures of 480?540°C, but decreases rapidly with increasing temperature in the range 540?640°C. As a function of Sb effusion cell temperature, the Sb mole fraction is shown to increase slightly slower than the Sb vapour pressure.     

Construction, Restoration, and Enhancement of 2 and 3-Dimensional Images

The construction of an image function from the physically measured projections of some object is discussed with reference to the least squares optimum filters, originally derived to enhance the signal-to-noise ratio in communications theory. The computerized processing associated with tomography is generalized so as to include 3 distinct parts: the construction of an image from the projection information, the restoration of a blurred, noisy image, degraded by a known space-invariant impulse response, and the further enhancement of the image, e.g. by edge sharpening. In conjuction with given versions of the popular convolution algorithm, not to be confused with filtering by a 2-dimensional convolution, we consider the conditions under which a concurrent construction, restoration, and enhancement are possible. Execution speeds are compared. ** Department of Electrical Science and Engineering, School of Engineering, University of California, Los Angeles, California 90024     

A 10 b, 20 Msample/s, 35 mW pipeline A/D converter

This paper describes a 10 b, 20 Msample/s pipeline A/D converter implemented in 1.2 μm CMOS technology which achieves a power dissipation of 35 mW at full speed operation. Circuit techniques used to achieve this level of power dissipation include digital correction to allow the use of dynamic comparators, and optimum scaling of capacitor values through the pipeline. Also, to be compatible with low voltage mixed-signal system environments, a switched capacitor (SC) circuit in each pipeline stage is implemented and operated at 3.3 V with a new high-speed, low-voltage operational amplifier and charge pump circuits. Measured performance includes 0.6 LSB of INL, 59.1 dB of SNDR (Signal-to-Noise-plus-Distortion-Ratio) for 100 kHz input at 20 Msample/s. At Nyquist sampling (10 MHz input) SNDR is 55.0 dB. Differential input range is ±1 V, and measured input referred RMS noise is 220 μV. The power dissipation at 1 MS/s is below 3 mW with 58 dB of SNDR     

Surface modification of rutile TiO2 by submerged arc discharge for improved photoreactivity

Titanium dioxide is well known for its photocatalytic activity, but it works effectively only in the ultraviolet (UV) range. Given the relatively low flux of solar UV that reaches earth, the potential of exploring its photocatalytic capacity for environmental protection applications is very limited. In this study, rutile, the least photocatalytic of the three existing titanium dioxide crystalline forms, was suspended in water or acetonitrile and treated with oxygen or argon plasmas, using a novel dense-medium plasma technology (submerged arc discharge). As a result of the plasma treatment, rutile particles were doped with various trace elements that originated in electrodes made of different metals. Subsequent analyses show that the photocatalytic capacity of plasma-modified rutile is comparable to or even better than that of unmodified anatase, the most photocatalytic form of titanium dioxides. The color change of TiO₂ samples after plasma treatment indicates that the modified rutile absorbs visible light and may therefore work as a photocatalyst in the visible range. Given the fact that rutile can be produced in large quantity more easily and cheaply than can anatase, these results are very encouraging and open up possibilities in using rutile for photocatalytic applications in the visible range. This paper was presented at the Third International Surface Engineering Congress and Exposition held August 2–4, 2004 in Orlando, FL.     

Texture investigation of copper interconnects with a different line width

To understand the effect of line width on textural and microstructural evolution of Cu damascene interconnect, three Cu interconnects samples with different line widths are investigated. According to x-ray diffraction (XRD) results, the (111) texture is developed in all investigated lines. Scattered {111}〈112〉 and {111}〈110〉 texture components are present in 0.18-μm-width interconnect lines, and the {111}〈110〉 texture was developed in 2-μm-width interconnect lines. The directional changes of the (111) plane orientation with increased line width were investigated by XRD. In addition, microstructure and grain-boundary character distribution (GBCD) of Cu interconnect were measured using electron backscattered diffraction (EBSD) techniques. This measurement demonstrated that a bamboo-like microstructure is developed in the narrow line, and a polygranular structure is developed in the wider line. The fraction of ∑3 boundaries is increased as the line width increases but is decreased in the blanket film. A new interpretation of textural evolution in damascene interconnect lines after annealing is suggested, based on the state of stress and growth mechanisms of Cu deposits.