A Compact Four-Wavelength Quantum-Cascade Laser Source

A four-wavelength quantum-cascade (QC) laser source that operates using a single current channel is presented. The source includes two different heterogeneous cascade QC lasers, one with emission wavelengths of 7.0 $mu{hbox {m}}$ and 11.2 $mu{hbox {m}}$, and the other with 8.7 $mu{hbox {m}}$ and 12.0 $mu{hbox {m}}$ . For 3.0-mm and 3.5-mm cavity lengths, QC lasers with emission wavelengths of 8.7, 11.2, and 12.0 $mu{hbox {m}}$ have threshold current densities within less than a factor of 2, which allows them to be conveniently driven in series by a single current source.      

A Center-Offset Polycrystalline-Silicon Thin-Film Transistor With ${rm n}^{+}$ Amorphous-Silicon Contacts

We have studied a bottom-gate polycrystalline-silicon thin-film transistor (poly-Si TFT) with amorphous-silicon (a-Si) ${rm n}^{+}$ contacts and center-offset gated structure, where intrinsic poly-Si is used in the center-offset region. The fabrication process is compatible with the conventional a-Si TFT with addition of thermal annealing for crystallization of a-Si. The bottom-gate poly-Si TFT with a 5-$muhbox{m}$ offset length exhibited a field-effect mobility of 18.3 $hbox{cm}^{2}/hbox{V} cdot hbox{s}$ and minimum OFF-state current of $hbox{2.79} times hbox{10}^{-12} hbox{A}/muhbox{m}$ at $V_{rm ds} = hbox{5} hbox{V}$. The leakage currents are two orders of magnitude lower than those of a nonoffset TFT with mobility drop from 23.8 to 18.3 $hbox{cm}^{2}/ hbox{V} cdot hbox{s}$.      

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 $mu{hbox {A}}$.      

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.      

Operation of Pt/AlGaN/GaN-Heterojunction Field-Effect-Transistor Hydrogen Sensors With Low Detection Limit and High Sensitivity

To enhance the device sensitivity and detection limit, a gate bias is applied to the catalytic metal of AlGaN/GaN-heterojunction field-effect-transistor (HFET) hydrogen sensors to control the carrier concentration in the channel at operation. The sensors exhibit a good sensitivity at temperatures up to 800 $^{circ}hbox{C}$ and a detection limit of 10-ppb $ hbox{H}_{2}$ in $hbox{N}_{2}$. The dependence of the device sensitivity on gate and drain biases has been investigated. The sensitivity peaks at the gate bias of threshold voltage and the drain bias of knee voltage in sensing gas. At high temperatures and $hbox{H}_{2}$ concentrations, specifically from 300 $^{circ}hbox{C}$ and 1000-ppm $hbox{H}_{2}/hbox{N}_{2}$, respectively, the sensitivity of HFETs at $V_{rm gs} = -hbox{3.5} hbox{V}$ and $V_{rm ds} = hbox{1} hbox{V}$ is more than three orders higher than their sensitivity at $V_{rm gs} = hbox{0} hbox{V}$ and the sensitivity of Schottky diodes.      

High Heat Flux Two-Phase Cooling in Silicon Multimicrochannels

This paper presents performances of two-phase cooling of a chip at very high heat flux with refrigerant R236fa in a silicon multimicrochannel heat sink. This heat sink was composed of 134 parallel channels, 67 $mu {hbox {m}}$ wide, 680 $mu {hbox {m}}$ high, and 20 mm long, with 92-$mu {hbox {m}}$ -thick fins separating the channels. The base heat flux was varied from 3 to 255 ${hbox {W/cm}}^{2}$ , the volume flow rate from 0.18 to 0.67 l/min, and the exit vapor quality from 0 to 80%. The working pressure and saturation temperature were set at 273 kPa and 25 $^{circ}{hbox {C}}$, respectively. The present database includes 1040 local heat transfer coefficients. The base temperature of the chip could be maintained below 52 $^{circ}{hbox {C}}$ while dissipating 255 ${hbox {W/cm}}^{2}$ with 10 $~^circ{hbox {C}}$ of inlet subcooling and 90 kPa of pressure drop. A comparison of the respective performances with an extrapolation of the present results shows that two-phase cooling should be able to cool the chip 13 K lower than liquid cooling for the same pumping power at a base heat flux of 350 ${hbox {W/cm}}^{2}$.      

Low-Threshold Strained Quantum-Well GaSb-Based Lasers Emitting in the 2.5- to 2.7-$mu$ m Wavelength Range

GaInAsSb–GaSb strained quantum-well (QW) ridge waveguide diode lasers emitting in the wavelength range from 2.51 to 2.72 $ mu{hbox {m}}$ have been grown by molecular beam epitaxy. The devices show ultralow threshold current densities of 44 $hbox{A}/{hbox {cm}}^{2}$ (${L}rightarrow infty $) for a single QW device at 2.51 $ mu{hbox {m}}$, which is the lowest reported value in continuous-wave operation near room temperature (15 $^{circ}hbox{C}$) at this wavelength. The devices have an internal loss of 3 ${hbox {cm}}^{-1}$ and a characteristic temperature of 42 K. By using broader QWs, wavelengths up to 2.72 $mu{hbox {m}}$ could be achieved.      

Q-Band pHEMT and mHEMT Subharmonic Gilbert Upconversion Mixers

This letter makes a comparison between Q-band 0.15 $mu{rm m}$ pseudomorphic high electron mobility transistor (pHEMT) and metamorphic high electron mobility transistor (mHEMT) stacked-LO subharmonic upconversion mixers in terms of gain, isolation and linearity. In general, a 0.15 $mu{rm m}$ mHEMT device has a higher transconductance and cutoff frequency than a 0.15 $mu{rm m}$ pHEMT does. Thus, the conversion gain of the mHEMT is higher than that of the pHEMT in the active Gilbert mixer design. The Q-band stacked-LO subharmonic upconversion mixers using the pHEMT and mHEMT technologies have conversion gain of $-$7.1 dB and $-$0.2 dB, respectively. The pHEMT upconversion mixer has an ${rm OIP}_{3}$ of $-$12 dBm and an ${rm OP}_{1 {rm dB}}$ of $-$24 dBm, while the mHEMT one shows a 4 dB improvement on linearity for the difference between the ${rm OIP}_{3}$ and ${rm OP}_{1 {rm dB}}$. Both the chip sizes are the same at 1.3 mm $times$ 0.9 mm.      

A Noise-Coupled Time-Interleaved Delta-Sigma ADC With 4.2 MHz Bandwidth, ${-}$ 98 dB THD, and 79 dB SNDR

This paper describes a wideband high-linearity $Delta Sigma $ ADC. It uses noise coupling combined with time interleaving. Two versions of a two-channel time-interleaved noise-coupled $Delta Sigma $ ADC were realized in a 0.18- $mu{hbox {m}}$ CMOS technology. Noise coupling between the channels increases the effective order of the noise-shaping loops, provides dithering, and prevents tone generation in all loops. Time interleaving enhances the effects of noise coupling. Using a 1.5 V supply, the device achieved excellent linearity (${rm SFDR} > {hbox {100~dB}}$, ${rm THD}= -{hbox {98~dB}}$) and an SNDR of 79 dB in a 4.2 MHz signal band.      

Electrical Instability of RF Sputter Amorphous In-Ga-Zn-O Thin-Film Transistors

Bias-temperature-stress (BTS) induced electrical instability of the RF sputter amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) was investigated. Both positive and negative BTS were applied and found to primarily cause a positive and negative voltage shift in transfer $(I _{rm DS} -V _{rm GS})$ characteristics, respectively. The time evolution of bulk-state density $(N _{rm BS})$ and characteristic temperature of the conduction-band-tail-states $(T _{G})$ are extracted. Since both values showed only minor changes after BTS, the results imply that observed shift in TFT $I _{rm DS} -V _{rm GS}$ curves were primarily due to channel charge injection/trapping rather than defect states creation. We also demonstrated the validity of using stretch-exponential equation to model both positive and negative BTS induced threshold voltage shift $(Delta V _{rm th})$ of the a-IGZO TFTs. Stress voltage and temperature dependence of $Delta V _{rm th}$ evolution are described.      

Tunable Linear MOS Resistors Using Quasi-Floating-Gate Techniques

A family of tunable MOS resistors based on quasi-floating-gate (QFG) transistors biased in the triode region is analyzed in this paper. From the study results, a new device that outperforms previous implementations, is presented. By means of a capacitive divider, the ac component of the drain-to-source voltage scaled with a factor $alphaleq 1$ is added to the gate-to-source voltage leading to a cancellation of the nonlinear terms. The effect of $alpha$ on resistor linearity is analytically studied. Simulation results are also provided for different technologies. Finally, a complete transconductor has been built which preserves the linearity of the MOS resistor. Three versions of the transconductor have been fabricated for different values of $alpha$ ($alpha=$ 0, 0.5, and 1) in a 0.5 $mu{hbox {m}}$ CMOS technology with $pm$1.65-V supply voltage. Experimental results show (for $alpha=1$ ) a THD of $-$ 57 dB $({rm HD}2=-70 {hbox {dB}})$ at 1 MHz for 2-V peak-to-peak differential input signal with a nominal ac-transconductance of 200 $muhbox{A/V}$ and a power consumption of 3.2 mW.      

AlGaN/GaN HEMTs With Low Leakage Current and High On/Off Current Ratio

In this letter, we propose using an oxide-filled isolation structure followed by $hbox{N}_{2}/hbox{H}_{2}$ postgate annealing to reduce the leakage current in AlGaN/GaN HEMTs. An off-state drain leakage current that is smaller than $hbox{10}^{-9} hbox{A/mm}$ (minimum $hbox{5.1} times hbox{10}^{-10} hbox{A/mm}$) can be achieved, and a gate leakage current in the range of $hbox{7.8} times hbox{10}^{-10}$ to $hbox{9.2} times hbox{10}^{-11} hbox{A/mm}$ ($V_{rm GS}$ from $-$10 to 0 V and $V_{rm DS} = hbox{10} hbox{V}$) is obtained. The substantially reduced leakage current results in an excellent on/off current ratio that is up to $hbox{1.5} times hbox{10}^{8}$. An improved flicker noise characteristic is also observed in the oxide-filled devices compared with that in the traditional mesa-isolated GaN HEMTs.      

Enhanced Transmission in a Fiber-Coupled Au Stripe Waveguide System

We experimentally demonstrated the enhanced transmission in a fiber-coupled Au stripe waveguide system using a linearly tapered (LT) structure at a telecommunication wavelength of 1.55 $mu{hbox {m}}$. The LT structure consists of two 100- $mu{hbox {m}}$-long tapered regions connecting various widths of input and output waveguides with a waist region. The lowest insertion loss of the 1-cm-long LT-Au stripe waveguide is $sim$4.3 dB, when it has 6-$mu{hbox {m}}$ -wide input and output waveguides and a 4- $mu{hbox {m}}$-wide waist waveguide. The insertion loss is reduced by $sim$ 2 dB compared to the 4-$mu{hbox {m}}$-wide and 1-cm-long straight Au stripe waveguide, which is achieved by decreasing the coupling loss. The losses of the LT region, which has a tapered angle of less than 0.3$^{circ}$ between the input–output waveguides and the waist waveguide, are smaller than 0.4 dB. We showed that the insertion loss of the Au stripe waveguide can be reduced by introducing the LT structure, which can also provide efficient mode conversion.      

A $Q$ -Band Four-Element Phased-Array Front-End Receiver With Integrated Wilkinson Power Combiners in 0.18-$mu{{hbox{m}}}$ SiGe BiCMOS Technology

A four-element phased-array front-end receiver based on 4-bit RF phase shifters is demonstrated in a standard 0.18- $mu{{hbox{m}}}$ SiGe BiCMOS technology for $Q$-band (30–50 GHz) satellite communications and radar applications. The phased-array receiver uses a corporate-feed approach with on-chip Wilkinson power combiners, and shows a power gain of 10.4 dB with an ${rm IIP}_{3}$ of $-$13.8 dBm per element at 38.5 GHz and a 3-dB gain bandwidth of 32.8–44 GHz. The rms gain and phase errors are $leq$1.2 dB and $leq {hbox{8.7}}^{circ}$ for all 4-bit phase states at 30–50 GHz. The beamformer also results in $leq$ 0.4 dB of rms gain mismatch and $leq {hbox{2}}^{circ}$ of rms phase mismatch between the four channels. The channel-to-channel isolation is better than $-$35 dB at 30–50 GHz. The chip consumes 118 mA from a 5-V supply voltage and overall chip size is ${hbox{1.4}}times {hbox{1.7}} {{hbox{mm}}}^{2}$ including all pads and CMOS control electronics.      

30-GHz Low-Noise Performance of 100-nm-Gate-Recessed n-GaN/AlGaN/GaN HEMTs

We demonstrate a 100-nm-gate-recessed n-GaN/AlGaN/GaN high-electron mobility transistor (HEMT) with low-noise properties at 30 GHz. The recessed GaN HEMT exhibits a low ohmic-contact resistance of 0.28 $Omega cdot hbox{mm}$ and a low gate leakage current of 0.9 $muhbox{A/mm}$ when biased at $V_{rm GS} = -hbox{3} hbox{V}$ and $V_{rm DS} = hbox{10} hbox{V}$. At the same bias point, a minimum noise figure of 1.6 dB at 30 GHz and an associated gain of 5 dB were achieved. To the best of our knowledge, this is the best noise performance reported at 30 GHz for gate-recessed AlGaN/GaN HEMTs.      

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.      

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.      

InGaAs/GaAs 0.98- $mu{hbox {m}}$ Low-Divergence Central-Lobe Semiconductor Lasers With $delta$ -Doped Resonant Tunneling Quantum Wells

In this paper, we describe a new structure design for producing low-threshold, high-efficiency, and high-brightness 0.98-$mu{hbox {m}}$ lasers. In this structure, we incorporated a self-discriminating weak optical confinement asymmetrical waveguide coupled to passive waveguides, and an active region based on three InGaAs quantum wells (QWs) coupled to Te n-type $delta$-doping. Optimized coupling between the $delta$-doping and the three QWs, together with waveguide optimization and doping profile optimization, yields $J_{rm th}=98 {hbox {A/cm}}^{2}$ per QW, ${T}_{0}=80;^{circ}hbox{C}$, and a far-field central lobe angle of $sim 10^{circ}$.      

Work-Function Engineering for 32-nm-Node pMOS Devices: High-Performance TaCNO-Gated Films

We have demonstrated p-type field effect transistors (p-FETs) devices using a TaCNO metal gate for the first time. These p-FETs have threshold voltage values of $-$ 0.4 and $-$ 0.25 V for HfSiON and HfSiO gate dielectrics, respectively, with equivalent oxide thickness of 1.6–1.7 nm. The TaCNO metal shows a high effective work function (eWF) of 4.89 eV on thick $hbox{SiO}_{2}$ interface layer, although the eWF rolls off with reducing EOT. Excellent transistor characteristics are achieved, with $I_{rm on}$ of $hbox{375} muhbox{A}/muhbox{m}$ at $I_{rm off} = hbox{60 nA}$, for $V_{rm dd} = hbox{1.1} hbox{V}$ .      

Strain Enhanced nMOS Using In Situ Doped Embedded $hbox{Si}_{1 - x}hbox{C}_{x}$ S/D Stressors With up to 1.5% Substitutional Carbon Content Grown Using a Novel Deposition Process

This letter reports on the implementation of high carbon content and high phosphorous content $hbox{Si}_{1 - x}hbox{C}_{x}$ layers in the source and drain regions of n-type MOSFET in a 65-nm-node integration scheme. The layers were grown using a novel epitaxial process. It is shown that by implementing stressors with $x approx hbox{0.01}$ , nMOSFET device performance is enhanced by up to 10%, driving 880 $mu hbox{A}/muhbox{m}$ at 1-V $V_{rm DD}$. It is also demonstrated that the successful implementation of $hbox{Si}_{1 - x} hbox{C}_{x}$ relies on the careful choice of integration and epitaxial layer parameters. There is a clear impact of the postepitaxial implantation and thermal treatment on the retained substitutional C content $([C_{rm sub}])$. Furthermore, adding a Si capping layer on top of the $hbox{Si}_{1 - x}hbox{C}_{x}$, greatly improves upon the stressors' stability during the downstream processing and the silicide sheet resistance.