Polarization-Independent Micro-Ring Resonator on Silicon-on-Insulator

Polarization-independent laterally-coupled micro-ring resonator has been designed and demonstrated. The origin of the polarization-sensitivity of the photonic wire waveguide (PWW) was analyzed. A polarization-insensitive PWW structure was designed and a polarization-insensitive MRR based on this PWW structure was designed by finite difference time-domain method and was fabricated on an 8-inch silicon-on-insulator wafer. The offset between the resonant wavelengths of the quasi-TE mode and the quasi-TM mode is smaller than 0.15 nm. The FSR is about 17 nm, extinction ratio about 10 dB and Q about 620.

Fabrication of Nano-structured VOx Film by Low Temperature Ion Beam Sputtering and Reductive Annealing

VOx thin films have been fabricated by low temperature ion beam sputtering and post reductive annealing process. Semiconductor-metal phase transition is observed for the film annealed at 400 degrees C for 2 hours. The film also shows a polycrystal structure with grain size from 50nm to 150nm. The VOx thin films fabricated by this process have a TCR up to -2.7% at room temperature. Our results indicate a promising fabrication method of the nano-structured VOx film with relatively high TCR and semiconductor-metal phase transition.

Low Temperature Deposited Nano-structured Vanadium Oxide Thin Films for Uncooled Infrared Detectors

A novel process of room temperature ion beam sputtering deposition of vanadium oxide films and low temperature post annealing for uncooled infrared detectors was proposed in this work. VOx thin films with relatively low square resistance (70 K Omega / square) and large temperature coefficient of resistance (more than 3%/K) at room temperature were fabricated using this low temperature process which was very compatible with the process of uncooled infrared detectors based on micromachined technology. Furthermore, chemical composition and film surface have been characterized using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) respectively. The results showed that the main composition of the processed thin films was V2O5 and the thin films were in the process of crystallization.

Observation of photogalvanic current for interband absorption in InN films at room temperature

The linear and circular photogalvanic effects have been observed in undoped InN films for the interband transition by irradiation of 1060 nm laser at room temperature. The spin polarized photocurrent depends on the degree of polarization, and changes its sip when the radiation helicity changes from left-handed to right-handed. This result indicates the sizeable spin-orbit interaction in the InN epitaxial layer and provides an effective method to generate spin polarized photocurrent and to detect spin-splitting effect in semiconductors with promising applications on spintronics.

Characteristics of triangle and square InP/InGaAsP microlasers

Directional emission triangle and square InGaAsP/InP lasers have been fabricated by standard photolithography, inductively coupled plasma etching technique combined with wet chemical etching process. In this article, the characteristics of the microcavity lasers are presented. For an equilateral triangle microcavity laser with the side length of 30 mu m, we got the laser spectra fitted very well with the mode wavelength formulate LIP to the 8(th) transverse mode at room temperature. But the laser spectra are usually more complex than the formulae for the lasers, especially for the lasers with a smaller side length. For a square microcavity laser with side length of 20 mu m, we observed the mode competition between the Fabry-Perot (FP) modes and Whispering-Gallery (WG) modes at 200K. The output spectra below the threshold have the mode interval of FP modes with a large mode interval, and the laser spectra agree very well with the WG modes, which have mode interval less than the FP modes. The output spectra are dominated by the FP modes below the threshold, because the FP modes have a higher output coupling efficiency than the WG modes.

A voltage-adjustable three-phase rectifier with constant power flow

An three phase adjustable output voltage rectifier with constant power flow based on waveform gap patching principle is resented. By patching the gapes in the phase currents in parallel way as well as the ripple of the output voltage in series way, it implements the constant power flow from the three-phase line to the DC output without using any line frequency (and its harmonics) energy storage components. Principally, by treating only 22.4% power of the needed power output, this rectifier can supply constant power flow with adjustable output voltages without bring about any harmonic interferences to the power utility and achieve unite power factor.

Hydrogen sensors based on Pt-AlGaN/GaN back-to-back Schottky diode

In this paper, platinum (Pt) with a thickness of 45 nm was sputtered on the surface of AlGaN/GaN heterostructure to form the Schottky contact and the back-to-back Schottky diodes were characterized for H-2 sensing at room temperature. Both the forward and reverse current of the devices increased with exposure to H-2 gas, which was attributed to Schottky barrier height reduction caused by hydrogen absorption in the catalytic metals. A shift of 0.7 V at 297 K was obtained at a fixed forward current of 0.1 mA after switching from N-2 to 40% H-2 in N-2. The sensor's responses under different concentrations from 2500 ppm H-2 to 40% H-2 in N-2 at 297 K were investigated. Time response of the sensor at a fixed bias of 1 V was given. Finally, the decrease of the Schottky barrier height and the sensitivity of the sensor were calculated. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

AlGaN/GaN/InGaN/GaN DH-HEMTs structure with an AlN interlayer grown by MOCVD

A novel AlGaN/GaN/GaN/GaN double heterojunction high electron mobility transistors (DH-HEMTS) structure with an AlN interlayer on sapphire substrate has been grown by MOCVD. The structure featured a 6-10 nm In0.1Ga0.9N layer inserted between the GaN channel and GaN buffer. And wer also inserted one ultrathin. AlN interlayer into the Al/GaN/GaN interface, which significantly enhanced the mobility of two-dimensional electron gas (2DEG) existed in the GaN channel. AFM result of this structure shows a good surface morphology and a low dislocation density, with the root-mean-square roughness (RMS) of 0.196 nm for a scan area of 5 mu m x 5 mu m. Temperature dependent Hall measurement was performed on this sample, and a mobility as high as 1950 cm(2)/Vs at room temperature (RT) was obtained. The sheet carrier density was 9.89 x10(12) cm(2), and average sheet resistance of 327 Omega/sq was achieved. The mobility obtained in this paper is about 50% higher than other results of similar structures which have been reported. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simulation of single electronic device and robust circuit construction

The article mainly focuses on the simulation of the single electron device and circuit. The orthodox model of single electronic device is introduced and the simulation with Matlab and Pspice is illustrated in the article. Moreover, the built of robust circuit using single electronic according to neural network is done and the simulation is also included in the paper. The result shows that neural network added with proper redundancy is an available candidate for single electron device circuit. The proposed structure is also promising for the realization of low ultra-low power consumption and solution of transient device failure.

Fracture properties of PECVD silicon nitride thin films by long rectangular memrane bulge test

Bulge test combined with a refined load-deflection model for long rectangular membrane was applied to determine the mechanical and fracture properties of PECVD silicon nitride (SiNx) thin films. Plane-strain modulus E-ps prestress s(0), and fracture strength s(max) of SiNx thin films deposited both on bare Si substrate and on SiO2-topped Si substrate were extracted. The SiNx thin films on different substrates possess similar values of E-ps and s(0) but quite different values of s(max). The statistical analysis of fracture strengths were performed by Weibull distribution function and the fracture origins were further predicted.

Fracture properties of silicon carbide thin films charcterized by bulge test of long membranes

The mechanical properties and fracture behavior of silicon carbide (3C-SiC) thin films grown on silicon substrates were characterized using bulge testing combined with a refined load-deflection model for long rectangular membranes. Plane-strain modulus E-ps, prestress so, and fracture strength s(max) for 3C-SiC thin films with thickness of 0.40 mu m and 1.42 mu m were extracted. The E, values of SiC are strongly dependent on grain orientation. The thicker SIC film presents lower so than the thinner film due to stress relaxation. The s(max) values decrease with increasing film thickness. The statistical analysis of the fracture strength data were achieved by Weibull distribution function and the fracture origins were predicted.

High Q-factor TM modes in three-dimensional semiconductor microresonators

We have investigated the mode characteristics for three-dimensional (3D) semiconductor microresonators by finite-difference time-domain (FDTD) technique. The results show that the quality-factors (Q-factors) of TM-like modes are much larger than those of TE-like modes as the vertical waveguidng formed by semiconductor materials.

Analysis of output coupling efficiencies for directional emission triangle and square microlasers

Output coupling efficiencies are analyzed for triangular and square microlasers connected with an output waveguide by FDTD simulation. The results show that square resonator with an output waveguide connected to the midpoint of one side can have high output coupling efficiency and a good mode selection.

The design and verification of FPGA CAD toolset

This paper introduces a complete CAD toolset for the implementation of digital logic in a Field-Programmable Gate Array (FPGA) platform. Compared with existing academic toolsets, this toolset introduces formal verification in each step of the tool flow, especially the formal verification of the configuration bitstream. The FPGA CAD tool verification flow using Formality is presented in detail. Using plug-in technology, we have developed an integrated FPGA design kit to incorporate all tools together.

Packing LUT clusters with network flow programming

This paper describes a two-step packing algorithm for LUT clusters of which the LUT input multipliers are depopulated. In the first step, a greedy algorithm is used to search for BLE locations and cluster inputs. If the greedy algorithm fails, the second step with network flow programming algorithm is employed. Numerical results illustrate that our two-step packing algorithm obtains better packing density than one-step greedy packing algorithm.