Microwave switch: LAMPS (light-activated microwave photoconductive switch)

A new microwave switch, the light-activated microwave photoconductive switch consisting of a heterostructure photoconductive switch (HPCS) with a flip-chip bonded vertical-cavity surface-emitting laser is reported. An insertion loss of 0.17 dB at a laser power of 15 mW and an isolation of 25 dB were obtained at 1 GHz. Excellent linearity was obtained with second and third order intercepts measured at 960 MHz of SOI=115 dBm and TOI=65 dBm at 960 MHz, respectively.     

Semisuperjunction MOSFETs: new design concept for lower on-resistance and softer reverse-recovery body diode

A new superjunction (SJ) structure offering remarkable advantages compared with the conventional SJ structure is proposed and demonstrated for a power-switching device. In the proposed structure (semi-SJ structure), an n-doped layer is connected to the bottom of the SJ structure. According to the results of experiment and simulation, the semi-SJ structure has both lower on-resistance and softer recovery of body diode than conventional SJ MOSFETs. The fabricated semi-SJ MOSFETs with breakdown voltage of 690 V realize on-resistance 28% lower than that of the conventional SJ MOSFET with same aspect ratio. The softness factor of the body diode is also improved by a factor of five. The proposed MOSFET is very attractive for H bridge topology applications, such as switching mode power supplies and small inverter systems, thanks to the low on-resistance and the soft recovery body diode.     

DNA Computing Boosted by a Cationic Copolymer

The huge information storage capability of DNA and its ability to self‐assemble can be harnessed to enable massively parallel computing in a small space. DNA‐based logic gates are designed that rely on DNA strand displacement reactions; however, computation is slow due to time‐consuming DNA reassembly processes and prone to failure as DNA is susceptible to degradation by nucleases and under certain solution conditions. Here, it is shown that the presence of a cationic copolymer boosts the speed of DNA logic gate operations that involve multiple and parallel strand displacement reactions. Two kinds of DNA molecular operations, one based on a translator gate and one on a seesaw gate, are successfully enhanced by the copolymer without tuning of computing conditions or DNA sequences. The copolymer markedly reduces operation times from hours to minutes. Moreover, the copolymer enhances nuclease resistance.     

Fabrication and current-drive of SiGe/Si 'Micro-origami' epitaxial MEMS device on SOI substrate

A micromirror structure with SiGe/Si heteroepitaxial layer on a silicon-on-insulator (SOI) substrate using a 'Micro-origami' technique has been successfully fabricated. The micromirror is supported by two curved hinge structures. The device is driven by application of a current, and net angular displacements larger than 10/spl deg/ (static) and 30/spl deg/ (in resonance) were obtained. These values are comparable with or even larger than the reported values for other MEMS optical switches or beam scanning devices. The experimental results suggest that the movement is evoked by a thermal effect. The Micro-origami device has advantages of low operation voltage smaller than 2 V, and structural compatibility with the Si or SiGe LSIs.     

Annealing effects of a high-quality ZnTe substrate

The sharp photoluminescence (PL) and optical-reflection spectra in the bandedge region of the high-quality nondoped ZnTe substrate (100) were observed at 4.2 K. Free exciton, associated with lower and upper polaritons (EX^L and EX^U) at 2.382 eV and 2.381 eV, respectively, were clearly observed. This meant that this substrate was high quality. The intensity of a bound exciton peak (2.375 eV), which is caused by a Zn vacancy, of a neutral acceptor decreased with an increase of the Zn vapor pressures.     

Fabrication of long-period fibre grating by CO/sub 2/ laser-annealing in fibre-drawing process

Long-period fibre grating (LPFG) writing by a CO₂ laser-annealing using a fibre-drawing process is demonstrated. The fibre in the drawing process was irradiated periodically by a CO₂ laser to modify the refractive index. An LPFG with transmission loss of -10 dB and full width at half-maximum of 13 nm has been fabricated. Results show that the refractive index change was induced by stress at the moment of laser annealing     

Durable Ultraflexible Organic Photovoltaics with Novel Metal‐Oxide‐Free Cathode

Flexible and stretchable organic photovoltaics (OPVs) are promising as a power source for wearable devices with multifunctions ranging from sensing to locomotion. Achieving mechanical robustness and high power conversion efficiency for ultraflexible OPVs is essential for their successful application. However, it is challenging to simultaneously achieve these features by the difficulty to maintain stable performance under a microscale bending radius. Ultraflexible OPVs are proposed by employing a novel metal‐oxide‐free cathode that consists of a printed ultrathin metallic transparent electrode and an organic electron transport layer to achieve high electron‐collecting capabilities and mechanical robustness. In fact, the proposed ultraflexible OPV achieves a power conversion efficiency of 9.7% and durability with 74% efficiency retention after 500 cycles of deformation at 37% compression through buckling. The proposed approach can be applied to active layers with different morphologies, thus suggesting its universality and potential for high‐performance ultraflexible OPV devices.     

Fibre transmission distance determined by eye opening degradation due to selfphase modulation and group-velocity dispersion

Numerical analysis of IM signal propagation in an optical fibre is carried out taking selfphase modulation and group-velocity dispersion into account. The transmission distance yielding a prescribed eye opening penalty, in the normal dispersion region, is shown to be inversely proportional to the square root of the signal power.<>     

Scanning and transmission electron microscopic studies on the upper and lower surfaces of the frog skin epidermal cells.

We examined the fine structure of the upper and lower surfaces of stratified squamous epithelial cells in the skin of frogs (Hyla japonica). SEM revealed the upper surface of superficial cells covered with ramified microridges (type 3). The width of the microridges was 0.20-0.24 microns. Microridges found at the cell boundary were about 0.30 microns in width and a narrow furrow was seen between the two cells. The numerous oval disk-like structures (0.23 x 0.32 microns in diameter) covered the lower surface of these superficial cells. The upper surface of cells in the 2nd layer was covered with baculiform or ramified microridges (type 2 or 3). On the cell boundary, two linear microridges (0.23-0.27 microns in width) were parallelly arranged. The width of the microridges covering the upper cell surface was 0.09-0.10 microns. Microvilli-like processes with a height of 0.32-0.37 microns were interspersed among the microridges. Their tip formed an oval plane (0.23 x 0.31 microns), which corresponded to the size of the disk-like structures on the lower surface of the superficial cells. Desmosomes were observed on the tip by TEM. These findings show that the disk-like structures on the lower surface of the superficial cells are the sites of binding with the microvilli-like processes on the upper surface of the 2nd layer cells. The disk-like structures observed in the present study seem to be equivalent to the binding site on the upper surface of the surface cell layer of mammalian stratified squamous epithelium.     

P-MOSFET's with ultra-shallow solid-phase-diffused drain structureproduced by diffusion from BSG gate-sidewall

A p-MOSFET structure with solid-phase diffused drain (SPDD) is proposed for future 0.1-μm and sub-0.1-μm devices. Highly doped ultrashallow p⁺ source and drain junctions have been obtained by solid-phase diffusion from a highly doped borosilicate glass (BSG) sidewall. The resulting shallow, high-concentration drain profile significantly improves short channel effects without increasing parasitic resistance. At the same time, an in situ highly-boron-doped LPCVD polysilicon gate is introduced to prevent the transconductance degradation which arises in ultrasmall p-MOSFETs with lower process temperature as a result of depletion formation in the p⁺-polysilicon gate. Excellent electrical characteristics and good hot-carrier reliability are achieved