Efficient Frequency Doubling of a Low-Power Femtosecond Er-Fiber Laser in BiB$_{3}$ O$_{6}$

BiB₃O₆ (BIBO) crystal has been used for efficient second-harmonic generation (SHG) of a low-power femtosecond Er-fiber laser-amplifier system operating at 56 MHz. At the maximum input power of 65 mW, an internal conversion efficiency of 23% was achieved for SHG at 782 nm, with a pulse duration of 64 fs. A comparison with beta-BaB₂O₄ reveals superior properties of BIBO for such ultrashort-pulse ultra-broadband SHG.     

Nitride-Based Asymmetric Two-Step Light-Emitting Diode With In$_{0.08}$ Ga$_{0.92}$ N Shallow Step

A nitride-based asymmetric two-step light-emitting diode (LED) with $hbox{In}_{0.08} hbox{Ga}_{0.92}hbox{N}$ shallow step was proposed and fabricated. It was found that the low indium content $hbox{In}_{0.08} hbox{Ga}_{0.92}hbox{N}$ layer can significantly enhance phase separation and/or inhomogeneous indium distribution in the active $hbox{In}_{0.27}hbox{Ga}_{0.73}hbox{N}$ layer. It was also found that we can enhance LED output power by a factor of 2.27 by simply inserting an $hbox{In}_{0.08} hbox{Ga}_{0.92}hbox{N}$ shallow step.      

Robust $H_{infty}$ Filtering for Switched Stochastic System With Missing Measurements

This paper considers the design of robust $H_{infty}$ filtering problem for switched stochastic discrete time-delay system with missing measurements via switched Lyapunov function approach. Attention is focused on the design of an exponentially stable filter guaranteeing a prescribed noise attenuation level in the $H_{infty}$ sense and missing measurements probability. By using switched Lyapunov functionals, some sufficient conditions in terms of linear matrix inequalities (LMIs) are obtained. Finally, a numerical example is provided to demonstrate the effectiveness and applicability of the proposed design approach.      

180$^{circ}$ and 90$^{circ}$ Phase Shifting Networks With an Octave Bandwidth and Small Phase Errors

A new phase shifting network for both 180 $^{circ}$ and 90 $^{circ}$ phase shift with small phase errors over an octave bandwidth is presented. The theoretical bandwidth is 67% for the 180$^{circ}$ phase bit and 86% for the 90$^{circ}$ phase bit when phase errors are $pm 2^{circ}$. The proposed topology consists of a bandpass filter (BPF) branch, consisting of a LC resonator and two shunt quarter-wavelength transmission lines (TLs), and a reference TL. A theoretical analysis is provided and scalable parameters are listed for both phase bits. To test the theory, phase shifting networks from 1 GHz to 3 GHz were designed. The measured phase errors of the 180$^{circ}$ and the 90$^{circ}$ phase bit are $pm 3.5^{circ}$ and $pm 2.5^{circ}$ over a bandwidth of 73% and 102% while the return losses are better than 18 dB and 12 dB, respectively.      

Diplexer With Integrated Filters and Photodetector in Ge–Si Using $Gamma-{X}$ and $Gamma-{M}$ Directions in a Grating Coupler

We demonstrate a central-office-type diplexer in which the filter and photodetector are monolithically integrated on a silicon-on-insulator substrate. The photonic integrated circuit receives a 1577-nm signal from an external laser and sends it to the fiber link using a two-dimensional grating coupler. The same grating coupler receives a 1270-nm signal from the fiber link and sends it to a monolithically integrated germanium photodetector using a polarization-diversity scheme to achieve polarization independence. The grating coupler is novel in that both the $Gamma-{X}$ and $Gamma-{M}$ directions are employed. This allows the grating coupler to couple both the 1577- and 1270-nm wavelengths with a small fiber tilt angle and hence have low polarization-dependent loss.      

Zn$_{1 - x}$Mg$_{x}$ O Homojunction-Based Ultraviolet Photodetector

Zn$_{1 - {x}}$ Mg$_{x}$ O p-n photodiodes were fabricated on (0001) sapphire substrates using a pulsed laser deposition technique with different Mg contents. Ti–Au and Ni–Au metals deposited using vacuum evaporation were used as n-type and p-type contacts, respectively. The X-ray diffraction analysis showed the Zn$_{1 - {x}}$Mg$_{x}$O double layers have a single phase hexagonal wurtzite structure. The optical bandgap of Zn$_{1 - {x}}$Mg$_{x}$O films has been tuned from 3.27 to 4.26 eV by increasing the Mg content ${x} =0.0$ to ${x}=0.34$. Correspondingly, the cutoff wavelength of the resultant detectors varies from 380 to 284 nm. Zn$_{1 - {x}}$Mg$_{x}$O p-n photodiodes with different Mg contents exhibit very good performance, with a very low dark current (${≪}$ 20 pA) at the bias voltage of 10 V. The ultraviolet to visible rejection ratio is more than three orders of magnitude.      

2 MHz AO $Q$ -switched ${rm TEM}_{00}$ Grazing Incidence Laser With 3 at.% Neodymium Doped Nd:YVO$_{4}$

We present a detailed experimental and theoretical study of the ultrahigh repetition rate AO $Q$ -switched ${rm TEM}_{00}$ grazing incidence laser. Up to 2.1 MHz $Q$-switching with ${rm TEM}_{00}$ output of 8.6 W and 2.2 MHz $Q$ -switching with multimode output of 10 W were achieved by using an acousto-optics $Q$ -switched grazing-incidence laser with optimum grazing-incidence angle and cavity configuration. The crystal was 3 at.% neodymium doped Nd:YVO$_{4}$ slab. The pulse duration at 2 MHz repetition rate was about 31 ns. The instabilities of pulse energy at 2 MHz repetition rate were less than ${pm}6.7hbox{%}$ with ${rm TEM}_{00}$ operation and ${pm}3.3hbox{%}$ with multimode operation respectively. The modeling of high repetition rate $Q$-switched operation is presented based on the rate equation, and with the solution of the modeling, higher pump power, smaller section area of laser mode, and larger stimulated emission cross section of the gain medium are beneficial to the $Q$-switched operation with ultrahigh repetition rate, which is in consistent with the experimental results.      

Impacts of $hbox{N}_{2}$ and $hbox{NH}_{3}$ Plasma Surface Treatments on High-Performance LTPS-TFT With High-$kappa$ Gate Dielectric

Low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs) with high- $kappa$ gate dielectrics and plasma surface treatments are demonstrated for the first time. Significant field-effect mobility $mu_{rm FE}$ improvements of $sim$86.0% and 112.5% are observed for LTPS-TFTs with $hbox{HfO}_{2}$ gate dielectric after $hbox{N}_{2}$ and $ hbox{NH}_{3}$ plasma surface treatments, respectively. In addition, the $hbox{N}_{2}$ and $ hbox{NH}_{3}$ plasma surface treatments can also reduce surface roughness scattering to enhance the field-effect mobility $mu_{rm FE}$ at high gate bias voltage $V_{G}$, resulting in 217.0% and 219.6% improvements in driving current, respectively. As a result, high-performance LTPS-TFT with low threshold voltage $V_{rm TH} sim hbox{0.33} hbox{V}$, excellent subthreshold swing S.S. $sim$0.156 V/decade, and high field-effect mobility $mu_{rm FE} sim hbox{62.02} hbox{cm}^{2}/hbox{V} cdot hbox{s}$ would be suitable for the application of system-on-panel.      

High-${Q}$ Transformers in Copper-Interconnection CMOS Technology

This paper proposes the adoption of aluminum-pad (AL-pad) film to improve the performance of on-chip transformers using current CMOS technology. Two devices proposed in this paper use an AL-pad film, without adding extra process, to enhance the Q value and bandwidth in the copper-interconnection process. The first device changes the transformer's coil location to increase the peak Q value and operation bandwidth, and the second device alters the coil material to improve the Q value in the entire operating band. A foundry 0.13-mum CMOS technology is fabricated the proposed transformers. The measurement results demonstrate that the first proposed device improves the peak Q value and operation bandwidth with the values of 32.5% and 22.6%, respectively. Afterward, the second proposed device increases the peak Q value 44.7% more than the standard device.     

A Comparative NBTI Study of $hbox{HfO}_{2}$, $hbox{HfSiO}_{x}$, and SiON p-MOSFETs Using UF-OTF $I_{rm DLIN}$ Technique

The time, temperature, and oxide-field dependence of negative-bias temperature instability is studied in $hbox{HfO}_{2}/hbox{TiN}$, $ hbox{HfSiO}_{x}/hbox{TiN}$, and SiON/poly-Si p-MOSFETs using ultrafast on-the-fly $I_{rm DLIN}$ technique capable of providing measured degradation from very short (approximately microseconds) to long stress time. Similar to rapid thermal nitrided oxide (RTNO) SiON, $hbox{HfO}_{2}$ devices show very high temperature-independent degradation at short (submilliseconds) stress time, not observed for plasma nitrided oxide (PNO) SiON and $hbox{HfSiO}_{x}$ devices. $hbox{HfSiO}_{x}$ shows lower overall degradation, higher long-time power-law exponent, field acceleration, and temperature activation as compared to $hbox{HfO}_{2}$, which are similar to the differences between PNO and RTNO SiON devices, respectively. The difference between $ hbox{HfSiO}_{x}$ and $hbox{HfO}_{2}$ can be attributed to differences in N density in the $hbox{SiO}_{2}$ IL of these devices.      

A Sub-$muhbox{W}$ Fully Tunable CMOS DPS for Uncooled Infrared Fast Imaging

This paper presents a very low-power and fully programmable CMOS digital active pixel sensor for uncooled IR fast imaging. The proposed circuit topology includes self-biasing, built-in input capacitance compensation, predictive A/D conversion, and a truly digital I/O interface, all at pixel level. Furthermore, full fixed pattern noise cancellation is also supplied by the external digital tuning of both offset and gain for each individual pixel at no speed costs. Two DPS circuit implementations for IR PbSe sensors have been integrated in standard 0.35-$mu{hbox {m}}$ 2-polySi 4-metal CMOS technology. Finally, exhaustive experimental results from their electrical tests are reported to validate the proposed DPS design techniques.      

Enhanced Vertical Light Extraction From Ultrathin Amorphous Si–Si$_{3}$ N$_{4}$ Multilayers With Photonic Crystal Patterns

We have investigated the significant enhancement of light extraction from amorphous Si-Si₃N₄ multiple-quantum-well structures, in which two-dimensional hexagonal-lattice air-hole photonic crystals (PCs) were integrated. The vertical spectral integrated intensity of light emission around 674 nm was enhanced up to times due to strong coupling to the inherent leaky modes or radiation modes near Gamma point of PC's band structure. The experimental observations also suggested that coupling to leaky modes should be more beneficial for light extraction enhancement.     

A 67 dBm $OIP_{3}$ Multistacked Junction Varactor

A multistacked varactor is presented for ultra-linear tunable radio frequency applications. The varactor elements are applied in anti-series configuration and are characterized by an “exponential” $C$- $V _{R}$ relationship. Third-order intermodulation ($IM_{3}$) is cancelled through proper harmonic loading of the terminals of the anti-series configuration. Multiple stacking is used to further increase the power handling and to minimize the remaining fifth-order distortion. The measured output intercept point ($OIP_{3}$ ) at 2 GHz is $ > 67~{rm dBm}$ for modulated signals up to 10 MHz bandwidth, while providing a capacitance tuning ratio of 3:1 with an average quality factor of 40 and maximum control voltage of 10 V.      

Eigendecomposition of Images Correlated on $S^{1}$, $S^{2}$, and $SO(3)$ Using Spectral Theory

Eigendecomposition represents one computationally efficient approach for dealing with object detection and pose estimation, as well as other vision-based problems, and has been applied to sets of correlated images for this purpose. The major drawback in using eigendecomposition is the off line computational expense incurred by computing the desired subspace. This off line expense increases drastically as the number of correlated images becomes large (which is the case when doing fully general 3-D pose estimation). Previous work has shown that for data correlated on S ¹ , Fourier analysis can help reduce the computational burden of this off line expense. This paper presents a method for extending this technique to data correlated on S ² as well as SO(3) by sampling the sphere appropriately. An algorithm is then developed for reducing the off line computational burden associated with computing the eigenspace by exploiting the spectral information of this spherical data set using spherical harmonics and Wigner-D functions. Experimental results are presented to compare the proposed algorithm to the true eigendecomposition, as well as assess the computational savings.     

Leakage Minimization of SRAM Cells in a Dual-$V_t$ and Dual-$T_{rm ox}$ Technology

Aggressive CMOS scaling results in low threshold voltage and thin oxide thickness for transistors manufactured in deep submicrometer regime. As a result, reducing the subthreshold and tunneling gate leakage currents has become one of the most important criteria in the design of VLSI circuits. This paper presents a method based on dual- V t and dual- T _ox assignment to reduce the total leakage power dissipation of static random access memories (SRAMs) while maintaining their performance. The proposed method is based on the observation that read and write delays of a memory cell in an SRAM block depend on the physical distance of the cell from the sense amplifier and the decoder. Thus, the idea is to deploy different configurations of six-transistor SRAM cells corresponding to different threshold voltage and oxide thickness assignments for the transistors. Unlike other techniques for low-leakage SRAM design, the proposed technique incurs neither area nor delay overhead. In addition, it results in a minor change in the SRAM design flow. The leakage saving achieved by using this technique is a function of the values of the high threshold voltage and the oxide thickness, as well as the number of rows and columns in the cell array. Simulation results with a 65-nm process demonstrate that this technique can reduce the total leakage power dissipation of a 64 times 512 SRAM array by 33% and that of a 32 times 512 SRAM array by 40%.     

Chalcogenide As$_{2}$S$_{3}$ Suspended Core Fiber for Mid-IR Wavelength Conversion Based on Degenerate Four-Wave Mixing

A chalcogenide optical fiber of special design is proposed to convert a short-wavelength infrared radiation (around 2 $mu$m) up to a second transparency window of atmospheric air (around 4.5 $mu$ m) by degenerate four-wave mixing. The fiber supports a small core surrounded by three large air holes. The zero-dispersion wavelength is shifted down to 2 $mu$m in this fiber by properly tailoring the fiber core. We demonstrate by solving the nonlinear SchrÖdinger equation that efficient wavelength-conversion can be obtained by pumping the fiber with a Tm : SiO$_{2}$ pulsed fiber laser.      

High-Performance $hbox{In}_{0.7}hbox{Ga}_{0.3}hbox{As}$ -Channel MOSFETs With High-$kappa$ Gate Dielectrics and $alpha$-Si Passivation

Long and short buried-channel $hbox{In}_{0.7}hbox{Ga}_{0.3}hbox{As}$ MOSFETs with and without $alpha$-Si passivation are demonstrated. Devices with $alpha$-Si passivation show much higher transconductance and an effective peak mobility of 3810 $hbox{cm}^{2}/ hbox{V} cdot hbox{s}$. Short-channel MOSFETs with a gate length of 160 nm display a current of 825 $muhbox{A}/muhbox{m}$ at $V_{g} - V_{t} = hbox{1.6} hbox{V}$ and peak transconductance of 715 $muhbox{S}/muhbox{m}$. In addition, the virtual source velocity extracted from the short-channel devices is 1.4–1.7 times higher than that of Si MOSFETs. These results indicate that the high-performance $hbox{In}_{0.7}hbox{Ga}_{0.3} hbox{As}$-channel MOSFETs passivated by an $alpha$ -Si layer are promising candidates for advanced post-Si CMOS applications.      

Pulsed $I_{d}$– $V_{g}$ Methodology and Its Application to Electron-Trapping Characterization and Defect Density Profiling

The pulsed current–voltage ($I$– $V$) measurement technique with pulse times ranging from $sim$17 ns to $sim$ 6 ms was employed to study the effect of fast transient charging on the threshold voltage shift $Delta V_{t}$ of MOSFETs. The extracted $Delta V_{t}$ values are found to be strongly dependent on the band bending of the dielectric stack defined by the high-$kappa$ and interfacial layer dielectric constants and thicknesses, as well as applied voltages. Various hafnium-based gate stacks were found to exhibit a similar trap density profile.      

InP DHBT Process in Transferred-Substrate Technology With $f_{t}$ and $f_{max}$ Over 400 GHz

In this paper, a double heterojunction bipolar transistor (DHBT) process has been developed in transferred-substrate (TS) technology to optimize high-frequency performance. It provides an aligned lithographic access to frontside and backside of the device to eliminate dominant transistor parasitics. The transistors of $hbox{0.8} times hbox{5}hbox{-}muhbox{m}^{2}$ emitter mesa feature $f_{t} = hbox{410} hbox{GHz}$ and $f_{max} = hbox{480} hbox{GHz}$ at a $hbox{BV}_{rm ceo} = hbox{5.5} hbox{V}$. Parallel to the device setup, a multilevel metallization scheme is established. It serves as construction kit for 3-D configurations of active and passive elements. High yield of the TS DHBTs, consistent large-signal modeling, and accurate simulation of complex passive elements have been demonstrated and have proved the availability of the technology for advanced millimeter-wave circuit design.