A Low-Voltage Mobility-Based Frequency Reference for Crystal-Less ULP Radios

The design of a 100 kHz frequency reference based on the electron mobility in a MOS transistor is presented. The proposed low-voltage low-power circuit requires no off-chip components, making it suitable for application in wireless sensor networks (WSN). After a single-point calibration, the spread of its output frequency is less than 1.1% (3$sigma $) over the temperature range from $-{hbox{22}},^{circ}{hbox{C}}$ to 85$,^{circ}{hbox{C}}$ . Fabricated in a baseline 65$~$nm CMOS technology, the frequency reference circuit occupies 0.11$ hbox{mm}^{2}$ and draws 34 $ muhbox{A}$ from a 1.2 V supply at room temperature.      

RF Power Measurements of InAlN/GaN Unstrained HEMTs on SiC Substrates at 10 GHz

Unstrained high-electron mobility transistors (HEMTs) were fabricated from InAlN/GaN on semi-insulating SiC substrates. The devices had 0.24-$muhbox{m}$ T-gates with a total width of $hbox{2} times hbox{150} muhbox{m}$. Final passivated performance values for these devices are $I_{max} = hbox{1279} hbox{mA/mm}$, $I_{rm DSS} = hbox{1182} hbox{mA/mm}$ , $R_{c} = hbox{0.43} Omega cdot hbox{mm}$, $rho_{s} = hbox{315} Omega/hbox{sq}$, $f_{T} = hbox{45} hbox{GHz}$, $f_{max({rm MAG})} = hbox{64} hbox{GHz}$, and $g_{m} = hbox{268} hbox{mS/mm}$. Continuous-wave power measurements at 10 GHz produced $P_{rm sat} = hbox{3.8} hbox{W/mm}$, $G_{t} = hbox{8.6} hbox{dB}$, and $hbox{PAE} = hbox{30}%$ at $V_{rm DS} = hbox{20} hbox{V}$ at 25% $I_{rm DSS}$ . To our knowledge, these are the first power measurements reported at 10 GHz for this material.      

$hbox{TiN/ZrO}_{2}$/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 $^{circ}hbox{C}$.      

Novel Design of a 2.5-GHz Fully Integrated CMOS Butler Matrix for Smart-Antenna Systems

This paper presents a novel design of monolithic 2.5-GHz 4 $,times,$4 Butler matrix in 0.18- $mu$m CMOS technology. To achieve a full integration of smart antenna system monolithically, the proposed Butler matrix is designed with the phase-compensated transformer-based quadrature couplers and reflection-type phase shifters. The measurements show an accurate phase distribution of ${hbox{45}}{pm}{hbox{3}}^{circ}, ~{hbox{135}} pm {hbox{4}}^{circ}, ~ -{hbox{45}} pm {hbox{3}}^{circ}, ~{hbox{and}}~ -{hbox{135}} pm {hbox{4}}^{circ}$ with amplitude imbalance less than 1.5 dB. The antenna beamforming capability is also demonstrated by integrating the Butler matrix with a 1$,times,$ 4 monopole antenna array. The generated beams are pointing to $-{hbox{45}}^{circ}, ~ -{hbox{15}}^{circ}$ , 15$^{circ}$, and 45$^{circ}$, respectively, with less than 1$^{circ}$ error, which agree very well with the predictions. This Butler matrix consumes no dc power and only occupies the chip area of 1.36 $,times,$1.47 mm$^{2}$ . To our knowledge, this is the first demonstration of the single-chip Butler matrix in CMOS technology.      

$S$ - and $C$ -Band Ultra-Compact Phase Shifters Based on All-Pass Networks

Ultra-compact phase shifters are presented. The proposed phase-shifting circuits utilize the lumped element all-pass networks. The transition frequency of the all-pass network, which determines the size of the circuit, is set to be much higher than the operating frequency. This results in a significantly small chip size of the phase shifter. To verify this methodology, 5-bit phase shifters have been fabricated in the $S$ - and $C$ -band. The $S$ -band phase shifter, with a chip size of 1.87 mm $,times,$0.87 mm (1.63 mm $^{2}$), has achieved an insertion loss of ${hbox{6.1 dB}} pm {hbox{0.6 dB}}$ and rms phase-shift error of less than 2.8$^{circ}$ in 10% bandwidth. The $C$ -band phase shifter, with a chip size of 1.72 mm $,times,$0.81 mm (1.37 mm $^{2}$), has demonstrated an insertion loss of 5.7 dB $pm$ 0.8 dB and rms phase-shift error of less than 2.3 $^{circ}$ in 10% bandwidth.      

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.      

Cooperative Quantum Cutting in Yb $^{3+}$–Tb $^{3+}$ Codoped Borosilicate Glasses

Quantum cutting down-conversion (DC) with the emission of two near-infrared photons for each blue photon absorbed is realized in $hbox{Yb}^{3+}hbox{–}hbox{Tb}^{3+}$ codoped borosilicate glasses. With the excitation of $hbox{Tb}^{3+}$ ion by a 484-nm monochromatic light, emission from the $^{2} hbox{F} _{5/2}rightarrow ^{2} hbox{F} _{7/2}$ transition of $hbox{Yb}^{3+}$ ions is observed and this emission is proved to originate from the DC between $hbox{Tb}^{3+}$ ions and $hbox{Yb}^{3+}$ ions. Results shows that maximum quantum efficiency reach as high as 153%, which is comparable with that in oxyfluoride glass ceramics in this system. With the advantages of excellent transparence, easy shaping, good stability, and low cost, $hbox{Yb}^{3+}hbox{–}hbox{Tb}^{3+}$ codoped borosilicate glasses are potentially used as down-converter layer in silicon-based solar cells.      

Effect of Gate Dopant Diffusion on Leakage Current in n+Poly-Si/HfO2 and Examination of Leakage Paths by Conducting Atomic Force Microscopy

The effect of gate dopant diffusion on leakage current has been investigated in $hbox{n}^{+}hbox{poly-Si}/hbox{HfO}_{2}$ capacitors. The $hbox{HfO}_{2}$ films with low gate doping concentration exhibited very low leakage currents, whereas the films with heavy gate doping concentration showed excessive leakage currents. Conducting atomic force microscopy was applied to examine the current images of the $hbox{HfO}_{2}$ films showing excessive leakage currents, and evident leakage paths with annular shape were observed. The leakage paths observed in the $hbox{HfO}_{2}$ films with heavy doping poly-Si gate may be related to the diffusion of the excessive dopant from the $hbox{n}^{+}$ poly-Si gate into the $hbox{HfO}_{2}$ , particularly through the grain boundaries in the films. This may significantly increase the leakage currents in the $hbox{n}^{+}hbox{poly-Si}/hbox{HfO}_{2}$ devices.      

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.      

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 $V_{rm dd} = hbox{1.1} hbox{V}$ .      

High Conversion Efficiency InP/InGaAs Strained Quantum Well Infrared Photodetector Focal Plane Array With 9.7 $mu$m Cut-Off for High-Speed Thermal Imaging

InP/InGaAs material system is an alternative to AlGaAs/GaAs for long wavelength quantum well infrared photodetectors (QWIPs). We demonstrate a large format (640 $times$ 512) QWIP focal plane array (FPA) constructed with the strained InP/InGaAs material system. The strain introduced to the structure through utilization of $hbox{In}_{0.48}hbox{Ga}_{0.52}hbox{As}$ (instead of $hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ ) as the quantum well material shifts the cut-off wavelength from $sim$8.5 to 9.7 $muhbox{m}$. The FPA fabricated with the 40-well epilayer structure yields a peak quantum efficiency as high as 12% with a broad spectral response $(Deltalambda/lambda_{rm p}=17%)$. The peak responsivity of the FPA pixels is 1.4 A/W corresponding to 20% conversion efficiency in the bias region where the detectivity is reasonably high ($2.6times 10^{10} hbox{cmHz}^{1/2}/hbox{W}$ , f/1.5, 65 K). The FPA providing a background limited performance temperature higher than 65 K (f/1.5) satisfies the requirements of most low integration time/low background applications where AlGaAs/GaAs QWIPs suffer from read-out circuit noise limited sensitivity due to lower conversion efficiencies. Noise equivalent temperature differences of the FPA are as low as 19 and 40 mK with integration times as short as 1.8 ms and 430 $muhbox{s}$ (f/1.5, 65 K).      

High-Density and Low-Leakage-Current MIM Capacitor Using Stacked $hbox{TiO}_{2}/hbox{ZrO}_{2}$ Insulators

We have fabricated high-$kappa hbox{Ni}/hbox{TiO}_{2}/hbox{ZrO}_{2}/ hbox{TiN}$ metal–insulator–metal (MIM) capacitors. A low leakage current of $hbox{8} times hbox{10}^{-8} hbox{A/cm}^{2}$ at 125 $^{circ}hbox{C}$ was obtained with a high 38- $hbox{fF}/muhbox{m}^{2}$ capacitance density and better than the $hbox{ZrO}_{2}$ MIM capacitors. The excellent device performance is due to the lower electric field in 9.5-nm-thick $hbox{TiO}_{2}/ hbox{ZrO}_{2}$ devices to decrease the leakage current and to a higher $kappa$ value of 58 for $ hbox{TiO}_{2}$ as compared with that of $hbox{ZrO}_{2}$ to preserve the high capacitance density.      

Electrical Properties of $hbox{Bi}_{5}hbox{Nb}_{3} hbox{O}_{15}$ Thin Film Grown on $hbox{TiN}/hbox{SiO}_{2}/ hbox{Si}$ at Room Temperature for Metal–Insulator–Metal Capacitors

Buckling was observed in $hbox{Bi}_{5}hbox{Nb}_{3}hbox{O}_{15}$ (BiNbO) films grown on $hbox{TiN}/hbox{SiO}_{2}/hbox{Si}$ at 300 $^{circ}hbox{C}$ but not in films grown at room temperature and annealed at 350 $^{circ}hbox{C}$. The 45-nm-thick films showed a high capacitance density and a low dissipation factor of 8.81 $hbox{fF}/muhbox{m}^{2}$ and 0.97% at 100 kHz, respectively, with a low leakage current density of 3.46 $hbox{nA}/hbox{cm}^{2}$ at 2 V. The quadratic and linear voltage coefficients of capacitance of this film were 846 $hbox{ppm}/hbox{V}^{2}$ and 137 ppm/V, respectively, with a low temperature coefficient of capacitance of 226 $hbox{ppm}/^{circ}hbox{C}$ at 100 kHz. This suggests that a BiNbO film grown on a $hbox{TiN}/ hbox{SiO}_{2}/hbox{Si}$ substrate is a good candidate material for high-performance metal–insulator–metal capacitors.      

Demonstration of Tunneling FETs Based on Highly Scalable Vertical Silicon Nanowires

This letter demonstrates a vertical silicon-nanowire (SiNW)-based tunneling field-effect transistor (TFET) using CMOS-compatible technology. With a $hbox{Si} hbox{p}^{+}{-}hbox{i}{-} hbox{n}^{+}$ tunneling junction, the TFET with a gate length of $sim$200 nm exhibits good subthreshold swing of $sim$ 70 mV/dec, superior drain-induced-barrier-lowering of $sim$ 17 mV/V, and excellent $I_{rm on} {-} I_{rm off}$ ratio of $sim!!hbox{10}^{7}$ with a low $I_{rm off} (sim!!hbox{7} hbox{pA}/muhbox{m})$. The obtained 53 $muhbox{A}/muhbox{m} I_{rm on}$ can be further enhanced with heterostructures at the tunneling interface. The vertical SiNW-based TFET is proposed to be an excellent candidate for ultralow power and high-density applications.      

A Low-Power Low-Cost Fully-Integrated 60-GHz Transceiver System With OOK Modulation and On-Board Antenna Assembly

A fully-integrated 60-GHz transceiver system with on-board antenna assembly is presented. Incorporating on-off keying (OOK) and low-cost antenna designs, this prototype demonstrates a low-power solution for multi-Gb/s wireless communication. The enhanced OOK modulator/demodulator obviates baseband and interface circuitry, revealing a compact solution. Two antenna structures, folded dipole and patch array, are employed to fully examine the performance. Designed and fabricated in 90-nm CMOS technology, the transmitter and the receiver consume 183 and 103 mW and occupy 0.43 and 0.68 ${hbox {mm}}^{2}$, respectively. With 4 $times$ 3 patch antenna array, the transceiver achieves error-free operation $({hbox{BER}}<10^{-12})$ for $2^{31}-1$ PRBS of 1 Gb/s over a distance of 60 cm.      

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.      

A Short Range, Low Data Rate, 7.2 GHz-7.7 GHz FM-UWB Receiver Front-End

A 9 mW FM-UWB receiver front-end for low data rate ( $≪$$ hbox{50~kbps}$), short range ( $≪$$hbox{10~m}$) applications operating in the ultra-wideband (UWB) band centered at 7.45 GHz is described in this paper. A single-ended-to-differential preamplifier with 30 dB voltage gain, a 1 GHz bandwidth FM demodulator, and a combined (preamp/demodulator) receiver front-end were fabricated in 0.25 $muhbox{m}$ SiGe:C BiCMOS and characterized. Measured receiver sensitivity is $-hbox{85.8~dBm}$ while consuming 9 mW from a 1.8 V supply, and $-hbox{83~dBm}$ consuming 6 mW at 1.5 V. 15-20 m range line-of-sight in an indoor environment is realized, justifying FM-UWB as a robust radio technology for short range, low data rate applications. Multi-user and interference capabilities are also evaluated.      

A Theoretical Comparison of the Breakdown Behavior of $hbox{In}_{0.52}hbox{Al}_{0.48}hbox{As}$ and InP Near-Infrared Single-Photon Avalanche Photodiodes

We study the breakdown characteristics and timing statistics of InP and $hbox{In}_{0.52}hbox{Al}_{0.48}hbox{As}$ single-photon avalanche photodiodes (SPADs) with avalanche widths ranging from 0.2 to 1.0 $mu{hbox {m}}$ at room temperature using a random ionization path-length model. Our results show that, for a given avalanche width, the breakdown probability of $hbox{In}_{0.52}hbox{Al}_{0.48}hbox{As}$ SPADs increases faster with overbias than InP SPADs. When we compared their timing statistics, we observed that, for a given breakdown probability, InP requires a shorter time to reach breakdown and exhibits a smaller timing jitter than $hbox{In}_{0.52}hbox{Al}_{0.48}hbox{As}$ . However, due to the lower dark count probability and faster rise in breakdown probability with overbias, $hbox{In}_{0.52}hbox{Al}_{0.48}hbox{As}$ SPADs with $hbox{avalanche} hbox{widths}leq 0.5 mu{hbox {m}}$ are more suitable for single-photon detection at telecommunication wavelengths than InP SPADs. Moreover, we predict that, in InP SPADs with $hbox{avalanche} hbox{widths}leq 0.3 mu{hbox {m}}$ and $hbox{In}_{0.52}hbox{Al}_{0.48}hbox{As}$ SPADs with $hbox{avalanche} hbox{widths}leq 0.2 mu{hbox {m}}$, the dark count probability is higher than the photon count probability for all applied biases.      

A Wideband PLL-Based G/FSK Transmitter in 0.18 $mu$m CMOS

A wideband phase-locked loop (PLL)-based G/FSK transmitter (TX) architecture is presented in this paper. In the proposed TX, the G/FSK data is applied outside the loop; hence, the data rate is not constrained by the PLL bandwidth. In addition, the PLL remains locked all the time, preventing the carrier frequency from drifting. In this architecture, the G/FSK modulation signal is generated from a proposed Sigma-Delta modulated Phase Rotator $(SigmaDelta{hbox{-PR}})$. By properly combining the multi-phase signals from the PLL output, the $SigmaDelta{hbox{-PR}}$ effectively operates as a fractional frequency divider, which can synthesize modulation signals with fine-resolution frequencies. The proposed $SigmaDelta{hbox{-PR}}$ adopts the input signal as the phase transition trigger, facilitating a glitch-free operation. The impact of the $SigmaDelta{hbox{-PR}}$ on the TX output noise is also analyzed in this paper. The proposed TX with the $SigmaDelta{hbox{-PR}}$ is digitally programmable and can generate various G/FSK signals for different applications. Fabricated in a 0.18 $muhbox{m}$ CMOS technology, the proposed TX draws 6.3 mA from a 1.4 V supply, and delivers an output power of $-$11 dBm. With a maximum data rate of 6 Mb/s, the TX achieves an energy efficiency of 1.5 nJ/bit.      

Forming Gas Annealing Characteristics of Germanium-on-Insulator Substrates

Large-area layer transfer of germanium-on-insulator (GeOI) substrates has been fabricated by ion-cut processes. Pseudo-MOSFET structure was employed to characterize interface trap density, interface fixed charge density, interface carrier mobility, and bulk carrier mobility of these GeOI substrates with various annealing conditions in forming gas ambient. High-temperature annealing in the vicinity of 500 $^{circ}hbox{C}$–600 $^{circ}hbox{C}$ has shown the best carrier mobilities, with the interface trap density and the interface fixed charge density as low as $hbox{10}^{10} hbox{q/cm}^{2}$. The extracted bulk hole mobility of the annealed GeOI is near 500 $hbox{cm}^{2}/( hbox{V} cdot hbox{s})$, which is higher than that of silicon [300 $hbox{cm}^{2}/(hbox{V} cdot hbox{s})$] at the same doping concentration level.