Si hetero-bipolar transistor with a fluorine-doped SiC emitter anda thin, highly doped epitaxial base

The effect of fluorine doping on SiC/Si heterojunction bipolar transistors (HBTs) is studied. The film properties of the fluorine-doped SiC and device characteristics of an HBT using the SiC emitter and a 50-nm-thick, highly doped epitaxial base (10¹⁹/cm³) are presented. The current gain is improved from 15 to 80 by doping with fluorine. The current gain is four times larger than that of a conventional poly-Si emitter homo-transistor with the same base structure. In spite of the very thin base, the Early voltage is over 100 V. Forward-bias tunneling current was hardly seen at the emitter-base junction. The fluorine appears to terminate the dangling bonds. The results show the possibility of fabricating transistors with a very thin, highly doped base     

High-power, tunable, high-repetition rate TEA-13C18O2 laser

The authors report the power enhancement of a high-repetition-rate TEA-¹³C¹⁸O₂ laser by substitution of rare ¹⁵N₂ isotope instead of ¹⁴N₂ and its tunable single-mode operation. Efficient, high-power operation with a maximum average power of 25 W (100 Hz) at a slope efficiency of 5.6%, which is improved by a factor of 2 by substitution of ¹⁵N₂ instead of ¹⁴N₂, has been successfully achieved from a discharge volume of 57.5 cm³ with an active length of 26 cm. In addition, high-power, tunable, single-mode operation has been achieved with a three-mirror cavity consisting of two mirrors and a Littrow grating     

Development of a measurement technique for ion distribution in an extended nanochannel by super-resolution-laser-induced fluorescence

Ion behavior confined in extended nanospace (10(1)-10(3) nm) is important for nanofluidics and nanochemistry with dominant surface effects. In this paper, we developed a new measurement technique of ion distribution in the nanochannel by super-resolution-laser-induced fluorescence. Stimulated emission depletion microscopy was used to achieve a spatial resolution of 87 nm higher than the diffraction limit. Fluorescein was used for ratiometric measurement of pH with two excitation wavelengths. The pH profile in a 2D nanochannel of 410 nm width and 405 nm depth was successfully measured at an uncertainty of 0.05. The excess protons, showing lower pH than the bulk, nonuniformly distributed in the nanochannel to cancel the negative charge of glass wall, especially when the electric double layer is thick compared to the channel size. The present study first revealed the ion distribution near the surface or in the nanochannel, which is directly related to the electric double layer. In addition, the obtained proton distribution is important to understand the nanoscale water structure between single molecules and continuum phase. This technique will greatly contribute to understanding the basic science in nanoscale and interfacial dynamics, which are strongly required to develop novel miniaturized systems for biochemical analysis and further applications.     

Analytical threshold voltage model for short channel double-gateSOI MOSFETs

Solving a two-dimensional (2-D) Poisson equation and assuming the minimum potential determines the threshold voltage, V_th, we derived a model for V_th of short channel double-gate SOI MOSFETs, and verified its validity by comparing with numerical data. We evaluated the threshold voltage lowering, ΔV_th, and subthreshold swing (S-swing) degradation with decreasing gate length L _G, and showed that we can design a 0.05-μm-L_G device with ΔV_th of less than 50 mV and an S-swing of less than 70 mV/decade if 10-nm-thick SOI is available     

Self-aligned control of threshold voltages in sub-0.2-μm MOSFETs

We propose a new method to control the threshold voltages (V_th) in sub-0.2 μm MOSFETs. The method suppresses V_th fluctuations caused by variations in the fabricated gate length. Our scheme is to change the concentration of the channel impurity according to the gate length by tilted ion implantation from two directions after the polysilicon gate formation. We show the feasibility of our process by two-dimensional (2-D) process and device simulations. Then we clarify that our scheme was realized in fabricated nMOSFETs. We also measured the V_th in numerous MOSFETs and show that our method can indeed suppress V_th fluctuations caused by variations in the fabricated gate length     

Continuous preparative method of relatively large and uniform polymer beads and their application to immobilization of urease

An apparatus for continuous preparative method of polymer beads was investigated. Monomer droplets formed in glycerol were continuously introduced to a rotating glass tube which was filled with warmed glycerol and polymerized. Polymer beads of around 4 mm diameter were obtained. As an application of the polymer beads, urease was immobilized on the beads and their properties were evaluated. Macroreticular type of beads prepared with a mixture of maleic anhydride, styrene, and divinylbenzene showed the highest enzymatic activity among the beads tested, and the urease immobilized beads could be successfully applied for determination of blood urea nitrogen in human sera.     

Ultrafast operation of Vth-adjustedp+-n+ double-gate SOI MOSFET's

To optimize the V_th of double-gate SOI MOSFET's, we fabricated devices with p⁺ poly-Si for the front-gate electrode and n⁺ poly-Si for the back-gate electrode on 40-nm-thick direct-bonded SOI wafers. We obtained an experimental V_th of 0.17 V for nMOS and -0.24 V for pMOS devices. These double-gate devices have good short-channel characteristics, low parasitic resistances, and large drive currents. For gates 0.19 μm long, front-gate oxides 8.2 nm thick, and back-gate oxides 9.9 nm thick, we obtained ring oscillator delay times of 43 ps at 1 V and 27 ps at 2 V. To our knowledge, these values are the fastest reported for this gate length with suppressed short-channel effects     

Precision lattice parameter measurements on doped indium phosphide single crystals

Precision lattice parameter measurements have been made for various dopants as a function of doping concentration in order to provide a basis for understanding the reduction in dislocation density in heavily doped crystals. For the two dopants, Zn and S, which most effectively reduce the dislocation density, a monotonic decrease in lattice parameter with concentration is found for concentrations up to the mid 10¹⁸ cm^-3 level. On the other hand, a slight increase in lattice parameter is found for doping with tin which dose not reduce the dislocation density.