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.      

N-Face GaN/AlGaN HEMTs Fabricated Through Layer Transfer Technology

We present a new method to fabricate N-face GaN/AlGaN high electron mobility transistors (HEMTs). These devices are extremely promising for ultrahigh frequency applications where low contact resistances and excellent carrier confinement are needed. In this letter, the N-face of a Ga-face AlGaN/GaN epilayer grown on Si(111) is exposed by removing the Si substrate. To provide mechanical support, prior to the substrate removal, the Ga-face of the wafer is bonded to a Si(100) carrier wafer. The resultant N-face GaN/AlGaN heterostructures exhibited record transport properties ($mu_{e} !=! hbox{1670} hbox{cm}^{2}/hbox{V}cdot hbox{s}$, $n_{s} !=! hbox{1.6} !times! hbox{10}^{13}/ hbox{cm}^{2}$, and $R_{rm sh} = hbox{240} Omega/hbox{sq}$ ). These excellent transport properties rendered N-face HEMTs with 30% higher maximum drain current than Ga-face HEMTs and good RF characteristics ($f_{T} = hbox{10.7} hbox{GHz} cdot muhbox{m}$ and $f_{max} = hbox{21.5} hbox{GHz}cdot muhbox{m}$), comparable to state-of-the-art Ga-face devices.      

High Microwave-Noise Performance of AlGaN/GaN MISHEMTs on Silicon With Gate Insulator Grown by ALD

High microwave-noise performance is realized in AlGaN/GaN metal–insulator semiconductor high-electron mobility transistors (MISHEMTs) on high-resistivity silicon substrate using atomic-layer-deposited (ALD) $hbox{Al}_{2}hbox{O}_{3}$ as gate insulator. The ALD $hbox{Al}_{2}hbox{O}_{3}/hbox{AlGaN/GaN}$ MISHEMT with a 0.25- $muhbox{m}$ gate length shows excellent microwave small signal and noise performance. A high current-gain cutoff frequency $f_{T}$ of 40 GHz and maximum oscillation frequency $f_{max}$ of 76 GHz were achieved. At 10 GHz, the device exhibits low minimum-noise figure $(hbox{NF}_{min})$ of 1.0 dB together with high associate gain $(G_{a})$ of 10.5 dB and low equivalent noise resistance $(R_{n})$ of 29.2 $Omega$. This is believed to be the first report of a 0.25-$muhbox{m}$ gate-length GaN MISHEMT on silicon with such microwave-noise performance. These results indicate that the AlGaN/GaN MISHEMT with ALD $hbox{Al}_{2}hbox{O}_{3}$ gate insulator on high-resistivity Si substrate is suitable for microwave low-noise applications.      

High-Temperature Microwave Performance of Submicron AlGaN/GaN HEMTs on SiC

The effect of temperature on the small-signal radio-frequency (RF) performance of submicron AlGaN/GaN high-electron-mobility transistors on SiC has been studied from room temperature (RT) up to 600 K. A relation between ambient and channel temperatures has been established by means of finite-element simulations. The thermal behavior of the intrinsic parameters $C_{rm gs}$, $C_{rm gd}$, $g_{m, {rm int}}$, and $g_{rm ds}$ has been extracted accurately from RF measurements by means of the small-signal equivalent circuit. Main dc parameters $(I_{D}, g_{m, {rm ext}})$ show reductions close to 50% between RT and 600 K, mainly due to the decrease in the electron mobility and drift velocity. In the same range, $f_{T}$ and $f_{max}$ suffer a 60% decrease due to the reduction in $g_{m, {rm ext}}$ and a slight increase of $C_{rm gs}$ and $C_{rm gd}$. An anomalous thermal evolution of $C_{rm gd}$ at low $I_{D}$ has been identified, which is indicative of the presence of traps.      

High-Performance 0.1-$muhbox{m}$ Gate AlGaN/GaN HEMTs on Silicon With Low-Noise Figure at 20 GHz

The realization of high-performance 0.1-$muhbox{m}$ gate AlGaN/GaN high-electron mobility transistors (HEMTs) grown on high-resistivity silicon substrates is reported. Our devices feature cutoff frequencies as high as $f_{T} = hbox{75} hbox{GHz}$ and $f_{rm MAX} = hbox{125} hbox{GHz}$, the highest values reported so far for AlGaN/GaN HEMTs on silicon. The microwave noise performance is competitive with results achieved on other substrate types, such as sapphire and silicon carbide, with a noise figure $F = hbox{1.2}{-}hbox{1.3} hbox{dB}$ and an associated gain $G_{rm ass} = hbox{8.0}{-}hbox{9.5} hbox{dB}$ at 20 GHz. This performance demonstrates that GaN-on-silicon technology is a viable alternative for low-cost millimeter-wave applications.      

High-Frequency ZnO Thin-Film Transistors on Si Substrates

Record microwave frequency performance was achieved with nanocrystalline ZnO thin-film transistors fabricated on Si substrates. Devices with 1.2-$muhbox{m}$ gate lengths and Au-based gate metals had current and power gain cutoff frequencies of $f_{T} = hbox{2.45} hbox{GHz}$ and $f_{max} = hbox{7.45} hbox{GHz}$ , respectively. Same devices had drain–current on/off ratios of $hbox{5} times hbox{10}^{10}$, exhibited no hysteresis effects and could be operated at a current density of 348 mA/mm. The microwave performances of devices with 1.2- and 2.1- $muhbox{m}$ gate lengths and 50- and 100-$muhbox{m}$ gate widths were compared.      

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.      

Gate-Recess Technology for InAs/AlSb HEMTs

The gate-recess technology for Si $delta$-doped InAs/AlSb high-electron-mobility transistors (HEMTs) has been investigated by combining atomic force microscopy (AFM) inspection of the gate-recess versus time with electrical device characterization. Deposition of the gate metal on the $hbox{In}_{0.5}hbox{Al}_{0.5}hbox{As}$ protection layer or on the underlying AlSb Schottky layer resulted in devices suffering from high gate-leakage current. Superior dc and high frequency device performance were obtained for HEMTs with an insulating layer between the gate and the Schottky layer resulting in a reduction of the gate leakage current $I_{G}$ by more than two orders of magnitude at a drain-to-source voltage $V_{DS}$ of 0.1 V. The existence of this intermediate insulating layer was evident from the electrical measurements. AFM measurements suggested that the insulating layer was due to a native oxidation of the AlSb Schottky layer. The insulated-gate HEMT with a gate length of 225 nm exhibited a maximum drain current $I_{D}$ higher than 500 mA/mm with good pinchoff characteristics, a dc transconductance $g_{m}$ of 1300 mS/mm, and extrinsic values for cutoff frequency $f_{T}$ and maximum frequency of oscillation $f_{max}$ of 160 and 120 GHz, respectively.      

Electrical Properties of Amorphous $hbox{Bi}_{5} hbox{Nb}_{3}hbox{O}_{15}$ Thin Film for RF MIM Capacitors

Amorphous $hbox{Bi}_{5}hbox{Nb}_{3}hbox{O}_{15}(hbox{B}_{5} hbox{N}_{3})$ film grown at 300 $^{circ}hbox{C}$ showed a high-$k$ value of 71 at 100 kHz, and similar $k$ value was observed at 0.5–5.0 GHz. The 80-nm-thick film exhibited a high capacitance density of 7.8 fF/$muhbox{m}^{2}$ and a low dissipation factor of 0.95% at 100 kHz with a low leakage-current density of 1.23 nA/ $hbox{cm}^{2}$ at 1 V. The quadratic and linear voltage coefficient of capacitances of the $hbox{B}_{5}hbox{N}_{3}$ film were 438 ppm/$hbox{V}^{2}$ and 456 ppm/V, respectively, with a low temperature coefficient of capacitance of 309 ppm/$^{circ}hbox{C}$ at 100 kHz. These results confirmed the potential of the amorphous $hbox{B}_{5}hbox{N}_{3}$ film as a good candidate material for a high-performance metal–insulator–metal capacitors.      

A 2.4–2.5 GHz WLAN Direct-Conversion Receiver Front-End With Low-Distortion Baseband Filters

Low-distortion I/Q baseband filters interface with a 2.5 GHz RF receiver front-end configured as a Gm-cell in a direct-conversion architecture targeted towards WLAN 802.11b application. The active I/Q current-mode filters use AC current to carry the large swing of both desired and blocker signals, relaxing the voltage headroom requirement to a 1.2 V supply. An on chip master–slave automatic tuner is used to lock the filter bandwidth to a precision 20 MHz reference crystal oscillator, resulting in a $≪ ,$3% tuning accuracy and $≪, $ 0.5% I/Q bandwidth matching. The receiver achieves a 3.2 dB DSB NF, ${-}$14 dBm out-of-band IIP3, and ${+}$ 27 dBm worst case IIP2, all referred to the LNA input, while drawing 30mA from a 2.7 V supply. The chip is fabricated in a 0.5 $mu$m 46 GHz $f_{T}$ SiGe BiCMOS process. The active area is 2.54 mm$^{2}$ .      

AlN/GaN Insulated-Gate HEMTs With 2.3 A/mm Output Current and 480 mS/mm Transconductance

High-electron mobility transistors (HEMTs) based on ultrathin AlN/GaN heterostructures with a 3.5-nm AlN barrier and a 3-nm $hbox{Al}_{2}hbox{O}_{3}$ gate dielectric have been investigated. Owing to the optimized AlN/GaN interface, very high carrier mobility $(sim!!hbox{1400} hbox{cm}^{2}/hbox{V}cdothbox{s})$ and high 2-D electron-gas density $(sim!!kern1pthbox{2.7} times hbox{10}^{13} /hbox{cm}^{2})$ resulted in a record low sheet resistance $(sim !!hbox{165} Omega/hbox{sq})$. The resultant HEMTs showed a maximum dc output current density of $simkern1pt$2.3 A/mm and a peak extrinsic transconductance $g_{m,{rm ext}} sim hbox{480} hbox{mS/mm}$ (corresponding to $g_{m,{rm int}} sim hbox{1} hbox{S/mm}$). An $f_{T}/f_{max}$ of 52/60 GHz was measured on $hbox{0.25} times hbox{60} muhbox{m}^{2}$ gate HEMTs. With further improvements of the ohmic contacts, the gate dielectric, and the lowering of the buffer leakage, the presented results suggest that, by using AlN/GaN heterojunctions, it may be possible to push the performance of nitride HEMTs to current, power, and speed levels that are currently unachievable in AlGaN/GaN technology.      

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.      

High-Performance N-Face GaN Microwave MIS-HEMTs With > 70% Power-Added Efficiency

A high-performance N-face GaN metal–insulator–semiconductor high-electron-mobility transistor was fabricated. A dual-AlN back-barrier scheme was developed using polarization engineering to provide a large total dipole moment, which allowed enhanced modulation doping for a higher 2-D electron gas density without parallel conduction. Devices with 0.6-$muhbox{m}$ gate length showed an $f_{T}$ and $f_{max}$ of 17 and 58 GHz, respectively. A highest power-added efficiency (PAE) of 71% at 4 GHz was measured in these devices with 20-V drain bias. At 28 V, an output power density of 6.4 W/mm with 67% PAE was achieved.      

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.      

Low Turn-On Voltage and High-Current $hbox{InP}/ hbox{In}_{0.37}hbox{Ga}_{0.63}hbox{As}_{0.89}hbox{Sb}_{0.11}/hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ Double Heterojunction Bipolar Transistors

We report on the dc and microwave characteristics of an $ hbox{InP/In}_{0.37}hbox{Ga}_{0.63}hbox{As}_{0.89}hbox{Sb}_{0.11}/hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ double heterojunction bipolar transistor grown by solid-source molecular beam epitaxy. The pseudomorphic $hbox{In}_{0.37}hbox{Ga}_{0.63}hbox{As}_{0.89}hbox{Sb}_{0.11}$ base reduces the conduction band offset $Delta E_{C}$ at the emitter/base junction and the base band gap, which leads to a very low $V_{rm BE}$ turn-on voltage of 0.35 V at 1 $hbox{A/cm}^{2}$ . A current gain of 125 and a peak $f_{T}$ of 238 GHz have been obtained on the devices with an emitter size of $hbox{1}times hbox{10} muhbox{m}^{2}$, suggesting that a high collector average velocity and a high current capability are achieved due to the type-II lineup at the InGaAsSb/InGaAs base/collector junction.      

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.      

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.      

Worst Case Power/Ground Noise Estimation Using an Equivalent Transition Time for Resonance

The nonmonotonic behavior of power/ground noise with respect to the transition time $t_{r}$ is investigated for an inductive power distribution network with a decoupling capacitor. The worst case power/ground noise obtained with fast switching characteristics is shown to be significantly inaccurate. An equivalent transition time that corresponds to resonance is presented to accurately estimate the worst case power/ground noise in the time domain. Furthermore, the sensitivity of the ground noise to the decoupling capacitance $C_{d}$ and parasitic inductance $L_{g}$ is evaluated as a function of the transition time. Increasing the decoupling capacitance is shown to efficiently reduce the noise for transition times smaller than twice the $LC$ time constant, $t_{r}leq 2sqrt {L_{g}C_{d}}$. Alternatively, reducing the parasitic inductance $L_{g}$ is shown to be effective for transition times greater than twice the $LC$ time constant, $t_{r}geq 2sqrt {L_{g}C_{d}}$. The peak noise occurs when the transition time is approximately equal to twice the $LC$ time constant, $t_{r}approx 2sqrt {L_{g}C_{d}}$ , referred to as the equivalent transition time for resonance.      

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

A 10:1 Unequal Wilkinson Power Divider Using Coupled Lines With Two Shorts

A novel unequal Wilkinson power divider is presented. A coupled-line section with two shorts is proposed to realize the high characteristic impedance line, which cannot be implemented by conventional microstrip fabrication technique due to fabrication limitation. The proposed coupled-line structure is compatible with single layer integration and can be easily designed based on an even-odd mode analysis. As a design example, a 10:1 Wilkinson power divider at 2 GHz is fabricated and measured. The measured $-10~{rm dB}$ bandwidth of $S_{11}$ is about 16%, and the isolation $S_{32}$ is better than $-20~{rm dB}$ . The measured amplitude balance between output port 2 and port 3 is between $-10.20~{rm dB}$ and $-9.52~{rm dB}$, and the corresponding phase difference is between 0$^{circ}$ and 4.6$^{circ}$.