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We have developed 0.1- $\mu \text{m}$ gate-length InAlN/GaN high electron-mobility transistors (HEMTs) for millimeter-wave (MMW) power applications, particularly at 71–76 and 81–86 GHz bands. The impacts of depth and width of the gate recess groove on electrical performance have been analyzed and compared. Competing passivation technologies, atomic layer deposition (ALD) aluminum oxide (Al2O3) and plasma-enhanced chemical vapor deposition (PECVD) SiN, have also been assessed in terms of dc, pulsed- $IV$ , and high-frequency characteristics. It has been found that while PECVD SiN-passivated HEMTs and the monolithic microwave integrated circuits slightly underperform their ALD Al2O3-passivated counterparts, their MMW power performance can be further boosted with the gate recess due to the improved aspect ratio and scaling characteristics. When biased at a drain voltage of 10 V, a first-pass two-stage power amplifier design based on recessed PECVD SiN-passivated 0.1- $\mu \text{m}$ depletion-mode devices has demonstrated an output power of 1.63 W with a 15% power-added efficiency at 86 GHz.

High-performance 0.1- $\mu \text{m}$ InAlN/GaN high electron-mobility transistors (HEMTs) have been successfully developed for power amplifiers operating at E-band (targeting 71–76 and 81–86-GHz bands). High maximum drain current of 1.75 A/mm and maximum extrinsic transconductance of 0.8 S/mm have been achieved for depletion-mode devices. Enhancement-mode HEMTs have also shown maximum drain current of 1.5 A/mm and maximum extrinsic transconductance of 1 S/mm. The selection of atomic layer deposition aluminum oxide (Al2O3) for device passivation enables a two-terminal breakdown voltage of $\sim 25$ V, excellent subthreshold characteristics as well as the pulsed- IV featuring little current collapse for both types of HEMTs. When biased at a drain voltage of 10 V, a first-pass two-stage power amplifier design based on 0.1- $\mu \text{m}$ depletion-mode devices has demonstrated an output power of 1.43 W with 12.7% power-added efficiency at 86 GHz, a level of performance that has been attained previously only by state-of-the-art counterparts based on AlGaN/GaN HEMTs at a much higher drain bias and compression level.

Whereas gate-length reduction has served as the major driving force to enhance the performance of GaAs- and InP-based high-electron mobility transistors (HEMTs) over the past three decades, the limitation of this approach begins to emerge. In this paper, we present a systematic evaluation of the impact of greatly reduced source-drain spacing on the performance of 50-nm asymmetrically recessed metamorphic HEMTs (MHEMTs). Extremely high extrinsic transconductance has been achieved over a wide drain bias range starting from as low as 0.1 V by reducing source-drain spacing to 0.5 μm with a self-aligned (SAL) ohmic process. The measured maximum extrinsic transconductance of 3 S/mm is a new record for all HEMT devices on a GaAs substrate and is equal to the best results reported for InP-based HEMTs. With the use of an asymmetric recess, SAL MHEMTs also demonstrate remarkable improvement in other major figures of merit, including off-state breakdown, on-state breakdown, subthreshold characteristics, ION/IOFF ratio, and the voltage gain over the other SAL HEMTs reported so far. However, they still, in a few respects, under perform the conventional devices typically with 2-μm source-drain spacing. In particular, the on-state breakdown of the SAL devices has been capped at approximately 2 V, even with a very wide asymmetric recess. It appears that the uniqueness of the SAL technology would best fit applications that require low voltage and/or low DC power consumption, which can be fully tapped only when the parasitic capacitance is also properly controlled with, e.g., a high stem gate process.

We report the design, fabrication and characterization of metamorphic high electron-mobility transistors (MHEMTs) with self-aligned ohmic electrodes. In this work, asymmetrically recessed 50-nm Γ-gates have been successfully used as the shadow mask for ohmic metal deposition. Extremely high extrinsic transconductance over a wide drain bias from 0.1 to 1.25 V can be made possible by fabricating devices with small gate-source spacing, small source-drain spacing, and the non-alloyed ohmic. Measured maximum extrinsic transconductance of 3 S/mm is a new record for all HEMT devices on GaAs and equals the best results from InP -based HEMTs. The same devices also show a voltage gain of 22, maximum stable gain of 10.8 dB at 110 GHz, and breakdown voltage of 4.3 V, which all are the highest among any self-aligned HEMTs based on InGaAs channel. The outstanding performance is the result of the seamless integration of the asymmetric gate recess and Γ-gate-based self-aligned ohmic process.

We have fabricated and characterized ultrashort gate-length metamorphic high-electron mobility transistors (HEMTs) optimized for high gain performance for millimeter- and submillimeter-wave applications. In this paper, we have systematically evaluated the impact of gate length in the range of 25-50 nm on the device performance by exploring epitaxial layer designs, gate-to-channel distances, and recess widths. The study shows the 25-nm devices underperform their 50-nm counterparts in most of the key figures of merit including output conductance, voltage gain, off-state breakdown, on-state breakdown, and, most importantly, the maximum stable gain. This observation is actually in good agreement with the state-of-the-art results published so far, which indicate that the best overall performance of HEMTs for millimeter- and submillimeter-wave applications comes from devices with gate lengths ranging from 35 to 50 nm. The 25-nm devices, on the other hand, appear to have difficulty in achieving the proper vertical scaling for optimum gain, which is limited by the minimum gate layer thickness necessary to retain good Schottky characteristics. This limitation may eventually be overcome with the adoption of new materials used as the gate layer that can be integrated into the HEMT fabrication process.

This paper reports a successful improvement of the low breakdown voltages in short gate-length metamorphic high electron-mobility transistors. The technical approach includes both the optimization of the epitaxial layer design and the selection of the proper gate recess scheme. By employing a novel epitaxial design (including a high indium composite channel and the double-sided doping) and an asymmetric gate recess, both the off-state and on-state breakdown voltages have been improved for 50-nm high-performance metamorphic high electron-mobility transistors. The results reported herein demonstrate that these devices are excellent candidates for ultra-high-frequency power applications.

We report the design, fabrication and characterization of ultrahigh gain metamorphic high electron-mobility transistors. In this letter, a high-yield 50-nm T-gate process was successfully developed and applied to epitaxial layers containing high indium mole fraction InGaAs channels grown on GaAs substrates. A unique gate recess process was adopted to significantly increase device gain by effectively suppressing output conductance and feedback capacitance. Coupled with extremely small 10 mum times 25 mum via holes on substrates thinned to 1 mil, we achieved a 13.5 dB maximum stable gain (MSG) at 110 GHz for a 30-mum gate-width device. To our knowledge, this is the highest gain performance reported for microwave high electron-mobility transistor devices of similar gate periphery at this frequency, and equivalent circuit modeling indicates that this device will operate at frequencies beyond 300 GHz.

We report the design, fabrication, and characterization of ultrahigh-gain metamorphic high-electron-mobility transistors (MHEMTs) with significantly enhanced breakdown performance. In this letter, an asymmetrically recessed 50-nm Gamma-gate process has been successfully applied to epitaxial designs with double-sided-doped InAs-layer-inserted channels grown on GaAs substrates. The critical gate recess width has been optimized for device performance, including transconductance, breakdown voltage, and gain. The employment of a device passivation process greatly minimizes the adverse impacts that the aggressive vertical and lateral scaling would have introduced for pursuing enhanced performance. As a result, we have achieved 1.9-S/mm transconductance and 800-mA/mm maximum drain current at a drain bias of 1 V, 9-V off-state breakdown voltage, approximately 3.5-V on-state breakdown voltage, and 14.2-dB maximum stable gain at 110 GHz. To our knowledge, this is a record combination of gain and breakdown performance reported for microwave and millimeter-wave HEMTs, making these devices excellent candidates for ultrahigh-frequency power applications.

The authors have used chemical vapor deposition to grow ternary tungsten-based diffusion barriers to determine if they exhibit properties similar to those of sputter-deposited ternaries. A range of different W-B-N compositions in a band of compositions roughly between 20 and 40% W were produced. The deposition temperature was low, 350 C, and the precursors used are well accepted by the industry. Deposition rates are high for a diffusion barrier application. Resistivities range from 200 to 20,000 {micro}{Omega}-cm, the films with the best barrier properties having {approximately}1,000 {micro}{Omega}-cm resistivities. Adhesion to oxides is sufficient to allow these films to be used as the adhesion layer in a tungsten chemical mechanical polishing plug application. The films are x-ray amorphous as-deposited and have crystallization temperatures of up to 900 C. Barrier performance against Cu has been tested using diode test structures. A composition of W{sub .23}B{sub .49}N{sub .28} was able to prevent diode failure up to a 700 C, 30 minute anneal. These materials, deposited by CVD, display properties similar to those deposited by physical deposition techniques.

This paper reviews recent progress in the development of GaAs Metamorphic HEMT (MHEMT) technology for microwave, millimeter-wave, and submillimeter-wave applications. Short gate-length (50-100 nm) Metamorphic High Electron Mobility Transistors have been optimized for high gain and low noise performance. Efforts to further improve performance, manufacturability, and verify reliability will be reported. We also describe the design and performance of low noise MMIC amplifiers based on this technology.

Poly-Si thin-film transistors (TFTs) have recently been introduced to commercial glass flat-panel displays. This letter presents a manufacturable process for fabricating poly-Si TFTs directly on plastic substrates that exceed TFT parameter requirements for active-matrix displays. Plastic sheets are laminated onto carrier wafers, to allow use of automated tools for manufacturing. In order to maintain adhesion through the whole process, the wafer temperature is kept below 105/spl deg/C. Laser crystallization is used to grow poly-Si, and a quarter-wavelength stack layer is deposited to protect plastic from the laser processing. In order to achieve state-of-the-art poly-Si TFTs on plastic, the gate oxide is optimized. Using a higher temperature anneal after delamination minimizes leakage currents.

Reactively sputtered from a W2B target, amorphous W-B-N thin films are investigated. The physical properties of the films, namely density, resistivity, crystallization behavior and reaction temperature with silicon, are given as functions of composition. Additionally, the films are assessed as diffusion barriers between silicon substrates and copper overlays. By I(V) measurements of shallow-junction diodes, a 100 nm W64B20N16 barrier prevents copper from reaching the silicon during an 800 °C, 30 min heat treatment in vacuum. W79B21 films are able to prevent diffusion into the diodes only up to 500 °C. High resolution transmission electron microscopy shows that W64B20N16 and W79B21 films are both marginally amorphous with local ordering of less than 1.5 nm.

High electron mobility transistors (HEMTs) with single-quantum-well active layers composed of pseudomorphic InGaAs on GaAs and InP substrates have yielded substantial performance enhancements relative to their lattice-matched equivalents. The higher cut-off frequencies possessed by these devices have enabled new applications to be realized in the millimeter wave spectrum which are not feasible with lattice-matched HEMTs. Also, the devices are beginning to displace GaAs field effect transistors in the microwave spectrum as a result of higher gain and power-added efficiency inherent to the pseudomorphic devices. These developments in transistors and parallel developments in other strained layer material systems and devices have been paced by a resurgence in research and development in the materials science and engineering of strained epitaxial layers.

This paper reports the scaling behaviors of 25-nm asymmetrically recessed metamorphic high electron-mobility transistors. By employing an optimized epitaxial design and an asymmetric gate recess, excellent off-state and on-state breakdown voltages have been have been demonstrated for 25-nm high-performance metamorphic high electronmobility transistors. The results reported herein demonstrate that these devices are excellent candidates for ultra-high-frequency power applications.

A Q-band MMIC power amplifier has been designed, processed, and measured with first pass success. Design parameters include 20 dBm power, 25 dB gain, 40 % PAE, input return loss of 10 dB and output return loss of 6 dB across 43.5 to 45.5 GHz. The MMIC design is based on the BAE Systems 0.1 μm MHEMT device, which has high gain and excellent PAE. The two-stage amplifier uses a 2-finger, 75 μm unit gate width, 0.1 μm gate length MHEMT device for the first stage and two 4-finger, 75 μm unit gate width, 0.1 μm gate length MHEMT devices for the output stage. Complete stabilization for both the even and odd mode is provided using feedback and resistors in critical locations of the circuit. The first stage is optimized for gain while the output stage is optimized for power and power-added efficiency (PAE). The complete MMIC amplifier measures 3.5 mm × 1.7 mm complete with dc blocks and dc biasing elements. Measured performance includes record high PAE of 46 % at 44.5 GHz, 24 dB small-signal gain, 1 dB compressed power of 18 dBm, and 3-dB compressed power of 20.5 dBm across the 43.5 to 45.5 GHz frequency band.

Nonhydrogenated, n-channel, low-temperature-processed, single-crystal Si thin-film transistors (TFTs) have been fabricated on Si thin films prepared via sequential lateral solidification (SLS). The device characteristics of the resulting SLS TFTs exhibit properties and a level of performance that are superior to polycrystalline Si-based TFTs and are comparable to similar devices fabricated on silicon-on-insulator (SOI) substrates or bulk-Si wafers. We attribute these high-performance device characteristics to the absence of high-angle grain-boundaries within the active channel portion of the TFTs.

A free-drifting buoy has been designed which incorporates an array of capacitance wave gauges, an anemometer , compass, and a vertical accelerometer. The buoy is intended to drift free of the influence of an attending ship and collect and log high frequency wave data for verification of radar remotely sensed imagery. Data collected is used to derive energy directional wave spectra for wavelengths between 10 and 100 cm and wave slope statistics for wave scales larger than 10

Poly-Si Thin-Film Transistors (TFTs) are currently used in commercial active-matrix displays. They provide superior performance with respect to their amorphous silicon counterparts and allow integration of driving electronics directly on the display glass plates.For several applications, it can be desirable to have active-matrix displays made on flexible substrates. However, a direct application of a standard TFT process to plastic substrates is not in general possible, mostly because of temperature limits and related dimensional stability issues. In addition, standard flat-panel manufacturing tools are not capable of automatically handling non-rigid floppy substrates.Therefore, a new process has to be developed, compatible with a suitable way of handling plastic substrates. A process was developed in which plastic sheets are laminated on glass carrier wafers and run through all the automated tools. A low-temperature process using excimer laser annealing is developed and optimized. High-quality TFT backplanes are manufactured with a pixel layout designed for active-matrix OLED (AMOLED) displays. Field-effect mobility in excess of 70 cm2Vs on p-channel TFTs are achieved, together with leakage currents lower than 2 pA per micron gate width.Challenges include low-temperature gate dielectric development, reduction of intrinsic film stress, protection of plastic from laser damage, and contact formation. Solutions to these challenges are discussed and TFT transfer characteristics on glass and plastic substrates are presented. Finally, images from prototype monochrome AMOLED displays are presented, with 64 × 64 pixels and 80-dpi resolution.

We have developed 0.1-/spl mu/m gate-length InAlAs-InGaAs-InP power HEMT's with record efficiency and power gain at 94 GHz. A 200 /spl mu/m gate-width device has produced 58 mW output power with 6.4 dB power gain and 33% power-added efficiency. The extrapolated f/sub max/ of 600 GHz is the highest reported to date for any transistor, and smaller, 30-/spl mu/m devices fabricated on the same wafer exhibit excellent noise figure (1.4 dB at 94 GHz), demonstrating the applicability of this technology to multifunction MMICs. >

We report the development of a V-band monolithic power amplifier based on 0.1 /spl mu/m gate-length pseudomorphic HEMT's. The two-stage amplifier has demonstrated record performance at 60 GHz on the first design pass: 272 mW output power with 9.4 dB power gain and 24% power-added efficiency. The amplifier was designed for high-reliability communications applications, with passivation, good linearity and excellent thermal properties, and has been fabricated on 3-in. wafers with high yield and excellent uniformity-on one typical wafer, consistency of MMIC output power is better than /spl plusmn/0.5 dB with an associated total yield through RF test of 58%. >

Quarter-micron InAlAs/InGaAs planar-doped HEMTs (high-electron-mobility transistors) lattice-matched to InP have exhibited state-of-the-art noise and gain performance at frequencies up to 94 GHz. Minimum noise figures of 0.5, 1.2, and 2.1 dB have been measured at 18, 60, and 94 GHz, respectively. Small signal gains as high as 15.4 and 12.0 dB have been obtained at 63 and 95 GHz, respectively. Using 0.25 mu m InP-based HEMTs, a V-band three-stage amplifier yields an average noise figure of 3.0 dB with a gain of 22.0 +or-0.2 dB from 60 to 65 GHz at W-band, a two-stage amplifier exhibits a noise figure of 4.5 dB with a gain of 10.2 dB at 90.4 GHz, and a three-stage amplifier shows a noise figure of 4.8 dB with a gain of 15.0 dB at 90.4 GHz. It is concluded that these results clearly show the great potential of InP-based HEMTs for high-performance millimeter-wave low-noise receiver applications. >

Doped-channel, 0.25- mu m-gate-length, InGaAs pseudomorphic HEMTs (high electron mobility transistors) have been developed which exhibit state-of-the-art power performance at millimeter-wave frequencies, with output power density of 0.93 W/mm and power-added efficiency of 41% at 44 GHz. Using these devices, two Q-band hybrid power amplifiers have been developed. A two-stage design has produced 108 mW output power gain with 9.5 dB and 26.5% power-added efficiency. A three-stage design produced 251 mW output power with 13.6 dB of gain and 26.8% power-added efficiency. The peak efficiency of the three-state amplifier was 31.3% when biased differently. The linear gain of these amplifiers was 12 and 20 dB respectively. It is concluded that these amplifiers are an attractive alternative for designers of future millimeter-wave transmitters. >

A 0.15- mu m-gate-length double-heterojunction pseudomorphic HEMT (high electron mobility transistor) that exhibits state-of-the-art power and noise performance is reported. Power results include record power-added efficiencies of 51%, 41% and 23% at 35, 60 and 94 GHz, respectively, and output powers of 139 mW at 60 GHz and 57 mW at 94 GHz. Measured minimum noise figures of 0.55 dB at 18 GHz and 1.8 dB at 60 GHz are reported. It is suggested that because of its demonstrated performance and continued rapid rate of improvement, the pseudomorphic HEMT should be the preferred transistor for a number of millimeter-wave applications, used either as a discrete device in high-performance hybrid amplifiers or integrated into GaAs-based MMICs (monolithic microwave integrated circuits). >

The authors report the development of short gate-length (0.15-0.25- mu m) HEMTs (high-electron-mobility transistors) with state-of-the-art noise and power performance. The three families of HEMTs-conventional GaAs/AlGaAs, pseudomorphic, and InP-based-are described and compared. The InP HEMTs offer the lowest noise figure: device noise figures of 0.3 dB at 18 GHz and 1.4 dB at 94 GHz have been measured, and multistage amplifiers with 1.7-dB noise figure at 62 GHz and 3.3 dB at 92 GHz are reported. Pseudomorphic HEMTs that exhibit the best power performance of any millimeter-wave transistor have been developed, with record output powers of 658, 125, and 57 mW at 35, 60, and 94 GHz, respectively, and power-added efficiency as high as 41% at 60 GHz. A 44-GHz pseudomorphic HEMT power amplifier has generated 0.25-W output power with 27% power-added efficiency and 14-dB power gain. Finally, the reliability of the various HEMT types is discussed. >

Short-gate-length high-electron-mobility transistors (HEMTs) are reported that have exhibited state-of-the-art low-noise performance at millimeter-wave frequencies; minimum noise figure of 1.2 dB at 32 GHz and 1.8 dB at 60 GHz from 0.25- mu m HEMTs. At Ka-band, a two-stage low-noise amplifier has demonstrated an average noise figure of 2 dB from 26.5 GHz to 37 GHz with a gain of 17 dB at 32 GHz. At V-band, a two-stage amplifier yielded a noise figure of 3.2 dB at 61 GHz with flat gain 12.7*0.5 dB from 59 GHz to 65 GHz. These devices are described and the potential for their future improvement is discussed. >

The relative importance of f/sub t/ and f/sub max/ in millimeter-wave evaluation is discussed. Also presented is a study of the variation of C/sub gs/ (input capacitance), C/sub gd/ (gate-drain feedback capacitance), g/sub m/ (peak transconductance), and g/sub o/ (output conductance) with the distance, L/sub gd/, between the metal edge and the n/sup +/ cap layer on the drain side of the device in ultrashort-gate-length HEMT (high-electron-mobility transistors). For this study, a 0.15- mu m-gate-length, double-recess pseudomorphic HEMT was fabricated that exhibits a maximum frequency of oscillation, f/sub max/, of 350 GHz. This value is the highest f/sub max/ reported for any transistor. A very high C/sub gs//C/sub gd/ of 76 and a large voltage gain, g/sub m//g/sub o/ of 75 are observed in the device. These exceptional results are attained primarily by increasing L/sub gd/ to 2.3 times the gate length. >

High-performance InAlAs/InGaAs planar-doped HEMTs (high-electron-mobility transistors) lattice-matched to InP have been fabricated with a 0.25- mu m T-gate. A maximum extrinsic transconductance g/sub m/ of 900 mS/mm, corresponding to an intrinsic g/sub m/ of 1640 mS/mm, was obtained at room temperature. RF measurements at 18 GHz yielded a minimum noise figure of 0.5 dB with an associated gain of 15.2 dB and a maximum stable gain of 20.9 dB. At 58 GHz, the devices exhibited a 1.2-dB minimum noise figure with an 8.5-dB associated gain. At 63 GHz, a maximum available gain of 15.4 dB was measured for a single-stage amplifier. This value, extrapolated to -6 dB/octave, yielded a maximum frequency of oscillation f/sub max/ of 380 GHz, which is the highest f/sub max/ ever reported for any transistor. A three-stage HEMT amplifier exhibited an average noise figure of 3.0 dB with a gain of 22.0+or-0.2 dB from 60-65 GHz. >

The development of InGaAs pseudomorphic high-electron mobility transistors (HEMTs) with state-of-the-art power performance at millimeter-wave frequencies is reported. Results given include maximum power-added efficiencies of 44% at 35 GHz and 36% at 44 GHz, output power of 100 mW with 22% efficiency and 3-dB gain at 60 GHz, and output power of 9 mW at 94 GHz. Preliminary reliability data are presented, and prospects for further improvement in performance-the realization of multifinger HEMTs capable of higher output power and reduction of gate length to 0.1 mu m-are discussed. >

InP-based high electron mobility transistors (HEMTs) developed have exhibited state-of-the-art low noise and power performance well up to W-band frequencies. High performance V- and W-band monolithic amplifiers based on these devices have also been developed. A full W-band InP three-stage monolithic microwave integrated circuit (MMIC) amplifier yields a measured noise matching and bias decoupling networks. A thorough design and analysis procedure was incorporated, including accurate characterization of the devices and circuit elements at W-band frequencies. The first pass success of these full band MMIC amplifiers indicates the importance of accurate device characterization and thorough circuit designs in millimeter wave monolithic IC development. >

The authors present preliminary results of the effort to develop C-band high power internally-matched GaAs-based pseudomorphic high electron mobility transistors (PHEMTs) power amplifiers. Previously developed 0.25 /spl mu/m/spl times/8 mm PHEMT chips had been selected as the building block of the power amplifiers. The single chip units are comprised of one 8 mm PHEMT chip and its input and output matching circuits. These parts are integrated into a small copper carrier. By combining four 8 mm chips with lumped elements and a distributed Wilkinson power divider/combiner, the units were assembled within the same type of carrier and delivered 20 W output power. >

The power performance of 0.25- mu m*8-mm double recessed GaAs-based pseudomorphic high electron mobility transistors (PHEMTs) at 4 GHz is reported. The 0.25- mu m-gate-length PHEMTs exhibit typical gate-to-drain breakdown voltage of more than 20 V, peak transconductance of 430 mS/mm, and maximum drain current density of 450 mA/mm. When the drain was biased up to 11 V, the device delivered 5.7-W output power with 12.6-dB power gain and 57% power-added efficiency (PAE). The device demonstrates an extremely broad drain bias range for efficient operation. It exhibits a maximum PAE of 72% with an output power of 4.1 W under a V/sub DS/=7 V condition. with 8-V drain bias, when the device was tuned for maximum output power, it delivered 4.3 W of P/sub 2dB/ with 15.4-dB power gain and 66% PAE. >

We report the DC and power results for 0.1 /spl mu/m gate-length double heterojunction InAlAs/InGaAs HEMTs with lattice-matched, pseudomorphic and p-type InGaAs channels. At 60 GHz, 0.1 /spl mu/m/spl times/50 /spl mu/m HEMTs with a lattice-matched channel yielded peak power-added efficiency (PAE) of 49% with power density of 0.30 W/mm and power gain of 8.6 dB. When biased and tuned for maximum output power, the devices delivered 20.6 mW output power (0.41 W/mm power density) with 45% PAE and 8.0 dB power gain. The p-channel devices exhibited a lower output power density and efficiency due to the low channel current. The 200 /spl mu/m wide devices with pseudomorphic channel demonstrated 50% PAE with 6.7 dB power gain and 0.30 W/mm power density. Furthermore, the 400 /spl mu/m wide pseudomorphic channel devices delivered an output power of 192 mW (0.48 W/mm power density) with 30% PAE and 4.4 dB power gain. These results represent the highest PAE and power gain ever reported for any transistor at 60 GHz. >

The DC and microwave power performance of both lattice-matched and pseudomorphic InAlAs/InGaAs/InP high electron mobility transistors HEMT lattice-matched to an InP substrate yielded peak power-added efficiency of 52% with power gain of 10.5 db and power density of 0.41 W/mm. When the HEMT was biased and tuned for maximum output power, a power density of 0.78 W/mm and power-added efficiency of 44% with 10.2 dB power gain were measured. At 60 GHz, a 0.15- mu m-gate-length and 50- mu m-gate-width InP-based HEMT with a pseudomorphic channel demonstrated 41% peak power-added efficiency with 7.2 dB power gain and 0.35 W/mm power density. A similar device also exhibited peak power-added efficiency of 26% with power gain of 4.9 dB and output power density of 0.2 W/mm at 94 GHz. >

Double-heterojunction InGaAs pseudomorphic HEMTs (high electron mobility transistors) with a 0.25 mu m gate-length have been integrated into a three-stage power amplifier MMIC (monolithic microwave integrated circuit) designed for the 34-36 GHz band. This first pass design exhibited a peak small-signal gain of 30 dB, a minimum output power of 200 mW with 20 dB associated gain, a power-added efficiency of greater than 18%, and a return loss of greater than 14 dB over the entire band. This performance was measured with the MMIC operating from a single 6 V DC supply. >

This paper focuses primarily on the development in our laboratory of InP-based HEMTs for high frequency analog applications, and, where possible, our work is placed in the context of the industry at large. Perhaps the single most significant new development reported is the increase in device f/sub max/ to a value of 600 GHz. Current activity on InP HEMTs is aimed at improving device reliability, developing devices with higher power and efficiency, integrating low noise and power devices into monolithic microwave integrated circuits (MMICs) and improving the producibility of InP HEMT devices and MMICs.

Additional sources of magnetic field will combine with the Earth's field and locally deflect a magnetic compass from the true magnetic, or compass, north. As a result, ships using automatic pilots based on the magnetic compass, may be deflected from their planned route. This paper considers monopolar HVDC submarine power cables as sources of magnetic field, and the effects they may have on ships' compasses, in particular, on the paths of ships near the cable which are navigating by autopilot using the magnetic compass for its reference.

The authors have used chemical vapor deposition to grow ternary tungsten-based diffusion barriers to determine if they exhibit properties similar to those of sputter-deposited ternaries. A range of different W-B-N compositions in a band of compositions roughly between 20 and 40% W were produced. The deposition temperature was low, 350 C, and the precursors used are well accepted by the industry. Deposition rates are high for a diffusion barrier application. Resistivities range from 200 to 20,000 {micro}{Omega}-cm, the films with the best barrier properties having {approximately}1,000 {micro}{Omega}-cm resistivities. Adhesion to oxides is sufficient to allow these films to be used as the adhesion layer in a tungsten chemical mechanical polishing plug application. The films are x-ray amorphous as-deposited and have crystallization temperatures of up to 900 C. Barrier performance against Cu has been tested using diode test structures. A composition of W{sub .23}B{sub .49}N{sub .28} was able to prevent diode failure up to a 700 C, 30 minute anneal. These materials, deposited by CVD, display properties similar to those deposited by physical deposition techniques.

High electron mobility transistors (HEMTs) based on the InAlAs/InGaAs heterostructure have been grown on InP by molecular beam epitaxy. At room temperature, typical sheet charge densities of 2.1–3.0×1012 cm−2 and Hall electron mobilities over 10000 cm2 /V-s are obtained. An electron mobility as high as 13000 cm2 /V-s is achieved with a pseudomorphic Iny Ga1−y As channel and a y value of 0.70.HEMTs with a T- or Γ-shaped gate and with gate lengths ranging from 0.1–0.25 urn have been fabricated. A record low noise figure of 0.7 dB with an associated gain of 8.6 dB at 62 GHz has been achieved with 0.1 μm Γ-gate devices, while T-gate devices exhibit a minimum noise figure of 1.2 dB with 7.2 dB associated gain at 94 GHz. Separately, a record fmax value of 455 GHz was determined by extrapolating at -6 dB/octave from the measured gain of 13.6 dB at 95 GHz.Power HEMTs using a double heterojunction structure exhibit a record peak power-added efficiency (P.A.E.) of 49% with 8.6 dB power gain and 0.30 W/mm power density measured at 60 GHz. When biased and tuned for maximum output power, our best 60 GHz output power density to date is 0.52 W/mm with 33% P.A.E. and 5.9 dB power gain using a single heterojunction HEMT scheme with pseudomorphic channel. A similar device also yields peak P.A.E. of 26% with 0.20 W/mm power density and 4.9 dB gain at 94 GHz. These results represent the highest P.A.E.S and power gains ever reported for any transistor at these frequencies.

The development of HEMTs based on the InAlAs/InGaAs/InP materials system for high-frequency analog applications is reported. Devices with 0.15- mu m gatelengths have demonstrated extrinsic transconductance of 1500 mS/mm and extrapolated maximum frequency of oscillation f/sub max/ greater than 450 GHz. The noise figure is the lowest of any room-temperature receiver technology over the 5 to 100 GHz frequency range. Prospects for power amplification are excellent: power-added efficiency of 41% has already been demonstrated at 60 GHz. The integration of these devices into monolithic microwave integrated circuits (MMICs) is discussed. >

The authors report 0.15- mu m gate length GaAs-based and InP-based InGaAs channel high-electron-mobility transistors (HEMTs) that have exhibited state-of-the-art noise and gain performance well up to 100 GHz. 94-GHz noise figures of 2.4 and 1.4 dB with gains of 5.4 and 6.5 dB have been measured from GaAs- and InP-based HEMTs, respectively. High-performance W-band multistage amplifiers have been built using these devices. A two-stage GaAs-based amplifier exhibits a noise figure of 4.2 dB with a gain of 9.7 dB at 93 GHz, and a three-stage amplifier yields a 4.5-dB noise figure with 14.8-dB gain at 94 GHz. The best two-stage amplifier built with InP-based HEMTs exhibits a minimum noise figure of 3.2 dB with a gain of 11.5+or-0.4 dB from 88 to 96 GHz. A noise figure as low as 3.3 dB with gain of 17.3+or-0.5 dB from 88 to 96 GHz has also been demonstrated from a three-stage amplifier. The characteristics and performance of both devices are presented. >

A process for through‐the‐wafer via hole connections to each individual source contact for monolithic microwave and millimeter wave integrated circuits and power high electron mobility transistors has been developed using reactive ion etching in Cl2/BCl3/Ar gas mixtures. Placing vias in this manner eliminates the need for source airbridges, which minimizes source inductance and results in increased gain and efficiency. The GaAs etch rate and resultant etch profiles have been studied as functions of bias voltage, gas mixture, flow rate, via mask dimension, and etch time.

High electron mobility transistors (HEMTs) based on the InAlAs/InGaAs heterojunction grown lattice matched to InP were fabricated with 0.15 μm T-shaped gates. The use of an undoped InGaAs cap layer in the epitaxial structure leads to excellent gate characteristics and very high transistor gain. At 95 GHz, a maximum available gain of 13.6 dB was measured. A maximum frequency of oscillation fmax of 455 GHz was obtained by extrapolating from 95 GHz at –6 dB/octave. This is the best reported gain performance for any transistor.

This paper will describe a 30-GHz monolithic low-noise balanced mixer which has been developed using an integrated bow-tie antenna to waveguide transition and low parasitic Mott diodes. The diodes and mixer circuit were developed using MBE material and were fabricated using a plated airbridge technology. Measurements on the diode at dc and RF showed that the zero bias junction capacitance was 0.025 pF and the series resistance was 10 Omega. A mixer conversion loss of 6 dB was measured at 30 GHz with an IF of 1 GHz.

Quarter-micron-gate-length high-electron-mobility transistors (HEMTs) have exhibited state-of-the-art low-noise performance at millimeter-wave frequencies, with minimum noise figures of 1.2 dB and 32 GHz and 1.8 dB at 60 GHz. At Ka-band, two-stage and three-stage HEMT low-noise amplifiers have demonstrated noise figures of 1.7 and 1.9 dB, respectively, with associated gains of 17.0 and 24.0 dB at 32 GHz. At V-band, two stage and three-stage HEMT amplifiers yielded noise figures of 3.2 and 3.6 dB, respectively, with associated gains of 12.7 and 20.0 dB and 60 GHz. The 1-dB-gain compression point of all the amplifiers is greater than +6 dBm. The results clearly show the potential of short-gate-length HEMTs for high-performance millimeter-wave receiver application. >

Quarter-micrometer gate-length high-electron-mobility transistors (HEMTs) for cryogenic low-noise application with very low light sensitivity have been developed. At room temperature, these exhibit a noise figure of 0.4 dB with associated gain of 15 dB at 8 GHz. At a temperature of 12.5 K the minimum noise temperature of 5.3+or-1.5 K has been measured at 8.5 GHz, which is the best noise performance observed to date for any microwave transistors. The results clearly demonstrate the potential for low-temperature low-noise applications. >

Analytical modeling of these very-short-channel HEMTs (high-electron-mobility transistors) using the charge-control model is given. The calculations performed using this model indicate a very high electron velocity in the device channel (3.2+or-0.2*10/sup 7/ cm/s) and clearly demonstrate the advantages of the planar-doped devices as compared to the conventional uniformly doped HEMTs. Devices with different air-bridged geometries have been fabricated to study the effect of the gate resistance on the sub-0.1- mu m HEMT performance. With reduced gate resistance in the air-bridge-drain device, noise figures as low as 0.7 and 1.9 dB were measured at 18 and 60 GHz, respectively. Maximum available gains as high as 13.0 dB at 60 GHz and 9.2 dB at 92 GHz, corresponding to an f/sub max/ of 270 GHz, have also been measured in the device. Using the planar-doped pseudomorphic structure with a high gate aspect-ratio design, a noise figure of less than 2.0 dB at 94 GHz is projected based on expected further reduction in the parasitic gate and source resistances. >

Room-temperature noise performance of high-electron-mobility transistors (HEMTs) has been studied by correlating the microwave/millimeter-wave noise figure with lower frequency model parameters. By comparing devices fabricated from various molecular-beam epitaxially grown wafers, it is found that devices with high transconductance at low drain current generally exhibit superior noise performance. In particular, an optimal noise figure of 1.8 dB has been obtained at 60 GHz with 6.4-dB associated gain for devices from the best wafer. The low thermal noise coefficient ( theta >

0.15- mu m-gate-length double-heterojunction pseudomorphic high electron mobility transistors (HEMTs) for which excellent millimeter-wave power and noise performance were achieved simultaneously are reported. The 50- mu m-wide HEMTs yielded record maximum power-added efficiencies of 51, 41, and 23% at 35, 60, and 94 GHz, respectively. Maximum output powers of 139 mW at 60 GHz and 57 mW at 94 GHz were also measured for 150- mu m-gate-width devices. Finally, minimum noise figures as low as 0.55 and 1.8 dB were measured at 18 and 60 GHz respectively. This is the best power and noise performance yet reported for passivated transistors at millimeter-wave frequencies. >

High electron mobility transistors (HEMT's) have been fabricated which demonstrate excellent millimeter-wave performance. A maximum extrinsic transconductance as high as 430 mS/mm, corresponding to an intrinsic transconductance of 580 mS/mm, was observed in these transistors. A unity current gain cutoff frequency f T as high as 80 GHz and a maximum frequency of oscillation f_{\max} of 120 GHz were projected for these HEMT's. At 40 GHz, a minimum noise figure of 2.1 dB with an associated gain of 7.0 dB has also been measured. These are the highest f_{T}, f_{\max} , and the best noise performance reported to date. The results clearly demonstrate the potential of HEMT's for millimeter-wave low-noise applications.

Secondary ion mass spectrometry (SIMS) analysis has been extensively used to study impurity contamination and dopant incorporation in the fabrication procedures for the permeable base transistor (PBT). As a result of these SIMS findings, the fabrication procedures have been modified to minimize contamination, and recent PBT microwave performance and wafer-to-wafer reproducibility have improved dramatically. Seven of eight recent wafers tested at microwave frequencies have yielded devices with extrapolated values of maximum frequency of oscillation (f max ) from 108 to 223 GHz, with devices from the other wafer having an extrapolated f max value of 50 GHz. The highest values obtained for maximum stable power gain were 21.3 dB at 18 GHz in one device and 14.1 dB at 26.5 GHz in another. These gains are better than or comparable to those of the best submicrometer-gatelength HEMTs and MESFETs reported to date.