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.      

In Vivo Evaluation of a Mechanically Oscillating Dual-Mode Applicator for Ultrasound Imaging and Thermal Ablation

Unresectable liver tumors are often treated with interstitial probes that modify tissue temperature, and efficacious treatment relies on image guidance for tissue targeting and assessment. Here, we report the in vivo evaluation of an interstitial applicator with a mechanically oscillating five-element dual-mode transducer. After thoroughly characterizing the transducer, tissue response to high-intensity ultrasound was numerically calculated to select parameters for experimentation in vivo. Using perfused porcine liver, B-mode sector images were formed before and after a 120-s therapy period, and M-mode imaging monitored the therapy axis during therapy. The time-averaged transducer surface intensity was 21 or 27 W/cm$^2$. Electroacoustic conversion efficiency was maximally 72 $pm$ 3% and impulse response length was 295 $pm$ 1.0 ns at $-$6 dB. The depth of thermal damage measured by gross histology ranged from 10 to 25 mm for 13 insertion sites. For six sites, M-mode data exhibited a reduction in gray-scale intensity that was interpreted as the temporal variation of coagulation necrosis. Contrast ratio analysis indicated that the gray-scale intensity dropped by 7.8 $pm ;$3.3 dB, and estimated the final lesion depth to an accuracy of 2.3 $pm ;$2.4 mm. This paper verified that the applicator could induce coagulation necrosis in perfused liver and demonstrated the feasibility of real-time monitoring.      

$N times N$ Cyclic-Frequency Router With Improved Performance Based on Arrayed-Waveguide Grating

We have developed an $N times N$ cyclic-frequency router with improved performance by employing two types of modified configuration; a uniform-loss and cyclic-frequency (ULCF) arrayed-waveguide grating (AWG) and an interconnected multiple AWG. We have demonstrated a compact 50-GHz-spacing 64 $,times,$64 ULCF-AWG router with low and uniform insertion losses of 5.4–6.8 dB and frequency deviations from the grid of less than $pm {8}~{rm GHz}$. We have also demonstrated a 100-GHz-spacing 8$,times,$8 interconnected multiple-AWG router with a practical configuration, very low and uniform insertion losses of 2.3–3.4 dB, and frequency deviations from the grid of less than $pm {6}~{rm GHz}$. We discuss the suitable or realizable scale $N$ of the two types of routers by comparison with a conventional AWG router in terms of optical and dimensional performance and productivity.      

Characterization and Modeling of RF-Performance $(f_{T})$ Fluctuation in MOSFETs

The fluctuation of RF performance (particularly for $f_{T}$ : cutoff frequency) in the transistors fabricated by 90-nm CMOS technology has been investigated. The modeling for $f_{T}$ fluctuation is well fitted with the measurement data within approximately 1% error. Low-$V_{t}$ transistors (fabricated by lower doping concentration in the channel) show higher $f_{T}$ fluctuation than normal transistors. Such a higher $f_{T}$ fluctuation results from $C_{rm gg}$ (total gate capacitance) variation rather than $g_{m}$ variation. More detailed analysis shows that $C_{rm gs} + C_{rm gb}$ (charges in the channel and the bulk) are predominant factors over $C_{rm gd}$ (charges in LDD/halo region) to determine $C_{rm gg}$ fluctuation.      

A Biphase Modulator Circuit for Impulse Radio-UWB Applications

This letter presents a circuit to provide binary phase shift keying to ultra-wideband (UWB) impulse transmitters. The circuit is based on a Gilbert-cell multiplier and uses active on-chip balun and unbalanced-to-balanced converters for single-ended to single-ended operation. Detailed measurements of the circuit show a gain ripple of $pm 1~{rm dB}$ at an overall gain of $-2~{rm dB}$, an input reflection below $-12~{rm dB}$, an output reflection below $-18~{rm dB}$, a group delay variation below 6 ps and a $-1~{rm dB}$ input compression point of more than 1 dBm in both switching states over the full 3.1–10.6 GHz UWB frequency range. A time domain measurement verifies the switching operation using an FCC-compliant impulse generator. The circuit is fabricated in a $0.8~mu {rm m}$ Si/SiGe HBT technology, consumes 31.4 mA at a 3.2 V supply and has a size of $510 times 490~mu{rm m}^{2}$ , including pads. It can be used in UWB systems using pulse correlation reception or spectral spreading.      

$hbox{TiN/ZrO}_{2}$/Ti/Al Metal–Insulator–Metal Capacitors With Subnanometer CET Using ALD-Deposited $hbox{ZrO}_{2}$ for DRAM Applications

We provide the first report of the structural and electrical properties of $hbox{TiN/ZrO}_{2}$/Ti/Al metal–insulator–metal capacitor structures, where the $hbox{ZrO}_{2}$ thin film (7–8 nm) is deposited by ALD using the new zirconium precursor ZrD-04, also known as Bis(methylcyclopentadienyl) methoxymethyl. Measured capacitance–voltage ($C$– $V$) and current–voltage ( $I$–$V$) characteristics are reported for premetallization rapid thermal annealing (RTP) in $hbox{N}_{2}$ for 60 s at 400 $^{circ}hbox{C}$, 500 $^{circ}hbox{C}$, or 600 $^{ circ}hbox{C}$. For the RTP at 400 $^{circ}hbox{C}$ , we find very low leakage current densities on the order of nanoamperes per square centimeter at a gate voltage of 1 V and low capacitance equivalent thickness values of $sim$ 0.9 nm at a gate voltage of 0 V. The dielectric constant of $ hbox{ZrO}_{2}$ is 31 $pm$ 2 after RTP treatment at 400 $^{circ}hbox{C}$.      

An Edge Missing Compensator for Fast Settling Wide Locking Range Phase-Locked Loops

An edge missing compensator (EMC) is proposed to approach the function of an ideal PD with $pm 2 ^{N-1} times 2pi $ linear range with $N$-bit EMC. A PLL implemented with a 9-bit EMC achieves 320 MHz frequency hopping within 10 $~mu{hbox {s}}$ logarithmically which is about 2.4 times faster than the conventional design. The reference spur of the PLL is ${-}{hbox {48.7~dBc}}$ and the phase noise is ${-}hbox{88.31~dBc/Hz}$ at 10 kHz offset with $K_{rm VCO}= -$ 2 GHz/V.      

An Analytical Method to Extract the Physical Parameters of a Solar Cell From Four Points on the Illuminated $J{-}V$ Curve

For a variety of solar cells, it is shown that the single exponential $J{-}V$ model parameters, namely—ideality factor $eta$ , parasitic series resistance $R_{s}$, parasitic shunt resistance $R_{rm sh}$, dark current $J_{0}$, and photogenerated current $J_{rm ph}$ can be extracted simultaneously from just four simple measurements of the bias points corresponding to $V_{rm oc}$, $sim!hbox{0.6}V_{rm oc}$, $J_{rm sc}$, and $sim! hbox{0.6}J_{rm sc}$ on the illuminated $J{-}V$ curve, using closed-form expressions. The extraction method avoids the measurements of the peak power point and any $dJ/dV$ (i.e., slope). The method is based on the power law $J{-}V$ model proposed recently by us.      

Monolithically Integrated DFB-EA for 100 Gb/s Ethernet

The world's first monolithically integrated distributed feedback laser and electroabsorption (EA) modulator with an expected $geq$100 GHz $-$3 dBe bandwidth suitable for 100 Gb/s operation with on–off keying is presented. The design of the EA modulator uses a traveling-wave structure with three active segments and a total active length of 180 $muhbox{m}$ resulting in $ sim$2.5 V peak-to-peak drive voltage for 10 dB optical extinction ratio and low electrical reflection.      

A Temperature-to-Digital Converter Based on an Optimized Electrothermal Filter

This paper describes the design of a CMOS temperature-to-digital converter (TDC). It operates by measuring the temperature-dependent phase shift of an electrothermal filter (ETF). Compared to previous work, this TDC employs an ETF whose layout has been optimized to minimize the thermal phase spread caused by lithographic inaccuracy. To minimize electrical phase spread, the TDC's front-end consists of a wide bandwidth gain-boosted transconductor. The transconductor's output current is then digitized by a phase-domain $Sigma Delta $ modulator whose phase-summing node is realized by a chopper demodulator. To minimize the residual offset caused by the demodulator's switching action, the demodulator is located at the virtual ground nodes established by the transconductor's gain-boosting amplifiers. Measurements on 16 samples (within one batch) show that the TDC has an untrimmed inaccuracy of less than $pm hbox{0.7} ,^{circ}hbox{C}$ ($3sigma $) over the military range ($- hbox{55} ,^{circ}hbox{C}$ to 125$ ,^{circ}hbox{C}$).      

Performance Improvement of N-Type $hbox{TiO}_{x}$ Active-Channel TFTs Grown by Low-Temperature Plasma-Enhanced ALD

We report on performance improvement of $n$-type oxide–semiconductor thin-film transistors (TFTs) based on $hbox{TiO}_{x}$ active channels grown at 250 $^{circ}hbox{C}$ by plasma-enhanced atomic layer deposition. TFTs with as-grown $hbox{TiO}_{x}$ films exhibited the saturation mobility $(mu_{rm sat})$ as high as 3.2 $hbox{cm}^{2}/hbox{V}cdothbox{s}$ but suffered from the low on–off ratio $(I_{rm ON}/I_{rm OFF})$ of $hbox{2.0} times hbox{10}^{2}$. $hbox{N}_{2}hbox{O}$ plasma treatment was then attempted to improve $I_{rm ON}/I_{rm OFF}$. Upon treatment, the $hbox{TiO}_{x}$ TFTs exhibited $I_{rm ON}/I_{rm OFF}$ of $hbox{4.7} times hbox{10}^{5}$ and $mu_{rm sat}$ of 1.64 $hbox{cm}^{2}/hbox{V}cdothbox{s}$, showing a much improved performance balance and, thus, demonstrating their potentials for a wide variety of applications such as backplane technology in active-matrix displays and radio-frequency identification tags.      

Anisotropic Transient and Stationary Electron Velocity in Bulk Wurtzite GaN

The theoretical calculation of transient electron velocity overshoot in wurtzite $c$-axis GaN indicates a higher transient overshoot peak for transport in the basal plane ( $Gammahbox{-}M$ and $Gamma hbox{-}K$) than along the growth direction ($Gammahbox{-}A$ ). Characteristic rise times for the transient overshoot peak are found to be shorter for transport along the $c$-axis. Stationary electron velocity is significantly larger for transport oriented in the basal plane than along the $c$ -axis. No significant anisotropy is observed, however, in either the transient or steady-state electron velocity as a function of field orientation within the basal plane itself. The higher peak transient and stationary velocities in the basal plane are directly attributable to the anisotropy of the electronic dispersion, which exhibits lower effective mass along the $Gammahbox{-}M$ and $Gammahbox{-}K$ directions and greater nonparabolicity along the $Gammahbox{-}A$ direction.      

Equivalent Circuit Model for the Gate Leakage Current in Broken Down $hbox{HfO}_{2}/hbox{TaN/TiN}$ Gate Stacks

We propose an equivalent circuit model for the post-breakdown (BD) current–voltage ( $I$–$V$) characteristics in $hbox{HfO}_{2}/hbox{TaN/TiN}$ gate stacks in n-MOSFETs. The model consists of two opposite-biased diodes with series resistances and a shunt leakage path. The circuit admits analytical solution using the Lambert $W$-function and is tested for both negative and positive gate biases in the voltage range of $-$1.5 to $+$1.5 V. We also show the versatility of the proposed approach to deal with the post-BD $I$– $V$ when source and drain contacts are grounded or floating and analyze the obtained results in terms of the charge available for conduction.      

17 GHz RF Front-Ends for Low-Power Wireless Sensor Networks

A 17 GHz low-power radio transceiver front-end implemented in a 0.25 $mu{hbox {m}}$ SiGe:C BiCMOS technology is described. Operating at data rates up to 10 Mbit/s with a reduced transceiver turn-on time of 2 $mu{hbox {s}}$, gives an overall energy consumption of 1.75 nJ/bit for the receiver and 1.6 nJ/bit for the transmitter. The measured conversion gain of the receiver chain is 25–30 dB into a 50 $Omega$ load at 10 MHz IF, and noise figure is 12 $pm$0.5 dB across the band from 10 to 200 MHz. The 1-dB compression point at the receiver input is $-$37 dBm and ${hbox{IIP}}_{3}$ is $-$25 dBm. The maximum saturated output power from the on-chip transmit amplifier is $-$1.4 dBm. Power consumption is 17.5 mW in receiver mode, and 16 mW in transmit mode, both operating from a 2.5 V supply. In standby, the transceiver supply current is less than 1 $mu{hbox {A}}$.      

Extraction of the Effective Mobility of $ hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ MOSFETs

The extraction of the effective mobility on $hbox{In}_{0.53} hbox{Ga}_{0.47}hbox{As}$ metal–oxide–semiconductor field-effect transistors (MOSFETs) is studied and shown to be greater than 3600 $hbox{cm}^{2}/hbox{V} cdot hbox{s}$. The removal of $C_{rm it}$ response in the split $C$–$V$ measurement of these devices is crucial to the accurate analysis of these devices. Low-temperature split $C$–$V$ can be used to freeze out the $D_{rm it}$ response to the ac signal but maintain its effect on the free carrier density through the substrate potential. Simulations that match this low-temperature data can then be “warmed up” to room temperature and an accurate measure of $Q_{rm inv}$ is achieved. These results confirm the fundamental performance advantages of $hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ MOSFETs.      

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.      

10-GHz and 20-GHz Channel Spacing High-Resolution AWGs on InP

This letter reports on 10-GHz and 20-GHz channel-spacing arrayed waveguide gratings (AWGs) based on InP technology. The dimensions of the AWGs are 6.8$,times,$8.2 mm$^{2}$ and 5.0$,times,$6.0 mm$^{2}$, respectively, and the devices show crosstalk levels of $-$12 dB for the 10-GHz and $-$17 dB for the 20-GHz AWG without any compensation for the phase errors in the arrayed waveguides. The root-mean-square phase errors for the center arrayed waveguides were characterized by using an optical vector network analyzer, and are 18 $^{circ}$ for the 10-GHz AWG and 28$^{circ}$ for the 10-GHz AWG.      

Cubic-Structured $hbox{HfO}_{2}$ With Optimized Doping of Lanthanum for Higher Dielectric Constant

It is demonstrated that $hbox{HfO}_{2}$ films can have much higher dielectric-constant values than the usual reported value of 20–24 by optimized incorporation of lanthanum element and crystallization to cubic structure. When $hbox{HfO}_{2}$ with 8% La is crystallized into cubic structure, the film exhibits the $kappa$ value of $sim$ 38 which is the highest among ever reported $hbox{HfO}_{2}$ -based high-$kappa$ dielectrics. The increased $kappa$ value of $ hbox{HfO}_{2}$ with 8% La enables the leakage current to be reduced more than one order of magnitude lower, compared to amorphous-phase $hbox{HfO}_{2}$ under the same electric field. The dependence of film thickness and annealing temperature on the cubic crystallization is also reported.      

Multi-Channel Field-Effect Transistor (MCFET)—Part I: Electrical Performance and Current Gain Analysis

Multi-Channel Field-Effect Transistor (MCFET) structures with ultralow $I_{ rm OFF}$ (16 $hbox{pA}/muhbox{m}$) and high $I_{rm ON}$ (N: 2.27 $ hbox{mA}/muhbox{m}$ and P: 1.32 $hbox{mA}/muhbox{m}$ ) currents are obtained on silicon on insulator (SOI) with a high-$ kappa$/metal gate stack, satisfying both low-standby-power and high-performance requirements. The experimental current gain of the MCFET structure is compared with that of an optimized planar FD-SOI reference with the same high-$kappa$/metal gate stack and is quantitatively explained by an analytical model. Transport properties are investigated, and the specific MCFET electrostatic properties are evidenced, in particular a higher $V_{rm Dsat}$ for MCFETs compared with the planar reference. Finally, through 3-D numerical simulations correlated with specific characterizations, the influence of the channel width on the electrical performance is analyzed. For narrow devices, the parasitic bottom channel increases the total drain current of the MCFET structure without degrading the electrostatic integrity.      

Temperature-Insensitive Dual-Comb Filter Based on Multimode Interference Ti : LiNbO $_{3}$ Waveguide

A temperature-insensitive dual-comb filter has been demonstrated for the first time by multimode interference based on a Ti : LiNbO$_{3}$ channel waveguide. The phase difference between comb filters was about 180 $^{circ}$. We only observed less than ${pm}$0.125-nm variation of the center wavelength of the filter during temperature change from 20 $^{circ}$C to 50 $^{circ}$C. The measured extinction ratio and channel spacing of the comb filter were about ${-}$25 dB and 3.2 THz, respectively.