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A new field-effect resistive hydrogen sensor, based on the current-voltage characteristics in the linear region of an AlGaAs-based psuedomorphic high-electron-mobility transistor structure and high hydrogen sensitivity of a palladium metal, is studied. This studied resistive sensor shows that it provides the promise for low-power GaAs-based electronic and microelectromechanical-system applications.

Two antimonide-based compound semiconductor (ABCS) microstrip monolithic microwave integrated circuits (MMICs), i.e., single- and three-stage ultra-low-power wideband 0.3-11-GHz low-noise amplifiers (LNAs) using 0.1-[micro]m gate-length InAs/AISb metamorphic high electron-mobility transistors (HEMTs), have been fabricated and characterized on a GaAs substrate. The single-stage wideband LNA demonstrated a typical associated gain of 16 dB (0.3-11 GHz) with less than a 1.7-dB noise figure (2-11 GHz) at 5-mW dc power dissipation, and the three-stage wideband LNA demonstrated a typical associated gain of 30 dB (0.3-11 GHz) with less than a 2.6-dB noise figure (2-11 GHz) at 7.5-mW dc power dissipation. We believe these wideband LNA MMICs demonstrate the lowest dc power consumption with the highest gain-bandwidth product of any MMIC to date. These results demonstrate the outstanding potential of ABCS HEMT technology for ultra-low-power wideband applications. Index Terms--Antimonide-based compound semiconductor (ABCS) high electron-mobility transistor (HEMT), InAs/AlSb heterostructure field-effect transistor (HFET), low-noise amplifier (LNA), low power, monolithic microwave integrated circuit (MMIC), ultra-wideband.

In this theoretical paper, the analysis of the effect that ON-state active-device resistance has on the performance of a Class-E tuned power amplifier using a shunt inductor topology is presented. The work is focused on the relatively unexplored area of design facilitation of Class-E tuned amplifiers where intrinsically low-output-capacitance monolithic microwave integrated circuit switching devices such as pseudomorphic high electron mobility transistors are used. In the paper, the switching voltage and current waveforms in the presence of ON-resistance are analyzed in order to provide insight into circuit properties such as RF output power, drain efficiency, and power-output capability. For a given amplifier specification, a design procedure is illustrated whereby it is possible to compute optimal circuit component values which account for prescribed switch resistance loss. Furthermore, insight into how ON-resistance affects transistor selection in terms of peak switch voltage and current requirements is described. Finally, a design example is given in order to validate the theoretical analysis against numerical simulation. Index Terms--Class E, high efficiency, ON-channel resistance, pseudomorphic high electron mobility transistor (pHEMT), RF/microwave amplifiers.

Low-frequency (LF) dispersive phenomena due to device self-heating and/or the presence of 'traps' (i.e., surface state densities and bulk spurious energy levels) must be taken into account in the large-signal dynamic modeling of III-V field-effect transistors when accurate performance predictions are pursued, since these effects cause important deviations between direct current (dc) and dynamic drain current characteristics. In this paper, a new model for the accurate characterization of these phenomena above their cutoff frequencies is presented, which is able to fully exploit, in the identification phase, large-signal current-voltage (I-V) measurements carried out under quasi-sinusoidai regime using a recently proposed setup. Detailed experimental results for model validation under LF small- and large-signal operating conditions are provided. Furthermore, the I-V model proposed has been embedded into a microwave large-signal pseudomorphic high electron-mobility transistor (pHEMT) model in order to point out the strong influence of LF modeling on the degree of accuracy achievable under millimeter-wave nonlinear operation. Large-signal experimental validation at microwave frequencies is provided for the model proposed, by showing the excellent intermodulation distortion (IMD) predictions obtained with different loads despite the very low power level of IMD products involved. Details on the millimeter-wave IMD measurement setup are also provided. Finally, IMD measurements and simulations on a K [alpha]-band highly linear power amplifier, designed by Ericsson using the Triquint GaAs 0.25-[micro]m pHEMT process, are shown for further model validation. Index Terms--Field-effect transistors (FETs), intermodulation distortion (IMD), nonlinear circuits, nonlinear distortion, semiconductor device modeling.

A new small-signal modeling approach applied to GaN-based devices is presented. In this approach, a new method for extracting the parasitic elements of the GaN device is developed. This method is based on two steps, which are: 1) using cold S-parameter measurements, high-quality starting values for the extrinsic parameters that would place the extraction close to the global minimum of the objective function for the distributed equivalent circuit model are generated and 2) the optimal model parameter values are searched through optimization using the starting values already obtained. The bias-dependent intrinsic parameter extraction procedure is improved for optimal extraction. The validity of the developed modeling approach and the proposed small-signal model is verified by comparing the simulated wide-band small-signal S-parameter, over a wide bias range, with measured data of a 0.5-[micro]m GaN high electron-mobility transistor with a 2 x 50 [micro]m gatewidth. Index Terms--Computer-aided analysis, GaN high electron-mobility transistor (HEMT), parameter extraction, semiconductor device modeling.

This paper describes RF-driven gate current effects on the dc/RF performance of 0.15-[micro]m (gate length) 2-mil (substrate thickness) GaAs pseudomorphic high-electron mobility transistor (pHEMT) monolithic microwave integrated circuit power amplifiers (PAs). High gate current is generated in PAs under RF drive at room temperature. A long-term lifetest of PAs with various gate currents induced by RF drive was performed to investigate the effect of RF-driven gate current on dc/RF performance in GaAs pHEMT PAs. Accordingly, an empirical model was developed to predict the dc/RF performance of V-band PA modules by the end of life (EOL). This information is crucial for system engineers in order to budget sufficient output power so that the system can still maintain performance capability by EOL. Index Terms--Focused-ion beam (FIB), hot carrier, impact ionization, pseudomorphic high-electron mobility transistor (pHEMT), RF drive, scanning transmission electron microscopy (STEM).

Based upon a unique junction pseudomorphic high electron-mobility transistor (J-pHEMT) device, a novel method of providing high-efficiency power amplifier (PA) power control for variable envelope modulation schemes is demonstrated for enhanced data rates for global system for mobile communications evolution and wide-band code division multiple access. This new technique, based upon the use of a linear PA, was extended to provide a simple, but highly effective method of PA efficiency enhancement based upon dynamic adaptive bias control. Together, the architecture allows for substantially higher efficiency levels compared with conventional linear solutions over the entire range of handset operating conditions, while avoiding the necessity for complex control loops and linearization schemes. Furthermore, it is shown that the characteristics of the J-pHEMT, when used with this architecture, can he exploited to facilitate an efficient and completely novel single-chip PA plus antenna switch to substantially reduce the RF complexity of a cellular handset. Index Terms--Adaptive bias control, enhanced data rates for global system for mobile communications (GSM) evolution (EDGE), envelope tracking, monolithic microwave integrated circuit (MMIC) power amplifiers (PAs), power control, pseudomorphic high electron-mobility transistor (pHEMT).

This paper presents an experimental high-efficiency class-F power amplifier (PA) design, which integrates Rhodes's efficient low-pass matching network topology with the charge conservative, robust, and accurate WREN/COBRA nonlinear pseudomorphic high electron-mobility transistor (pHEMT) model for optimal drain efficiency. Large-signal model verification is undertaken where one-tone, load-pull, and wireless code-division multiple-access baseband time-domain tests are compared for simulated and experimental cases. Following a detailed theoretical analysis, a class-F matching network is proposed that suppresses the necessary load harmonics and delivers maximum drain efficiency. Utilizing the GaAs pHEMT model in computer-aided design, a microstrip matching network layout was generated and built at 2 GHz. The drain efficiency recorded for the first-pass effort was 70.5% with the use of no post-fabrication circuit tuning. Excellent agreement is also observed between the PAs simulated and measured performance, thus highlighting the advantages of an accurate device model in PA design. Index Terms--Amplifier, class F, nonlinear modeling, pseudomorphic high electron-mobility transistor (pHEMT).

This paper presents an empirical table-based nonlinear HEMT model fully extracted from time-domain large-signal measurements. A simple and direct extraction procedure, based on a vector nonlinear network analyzer measurement system with load-pull facilities, demonstrates by experimental results on microwave transistors how a very reduced number of measurements is enough to obtain the current and charge generators to fill a lookup model. Table-based model extraction, implementation, and validation are described in this paper. Index Terms--Field-effect transistors (FETs), modeling, MODFETs.

We report two resistive mixers, i.e., a balanced and a balanced image-rejection (IR) mixer for the 60-GHz frequency range. A compact and wide-band method for the local-oscillator (LO) power division is presented. The 56-GHz LO signal, which propagates in a coplanar-waveguide mode, is divided in between the lines of two spiral baluns. Consequently, a smooth and compact transition from even-to-odd propagation mode and an in-phase power division for two singly balanced unit mixers is achieved. As a result, the developed IR mixer occupies only 1.41[mm.sup.2] of chip area. The balanced design achieved 11.5 dB of conversion loss from 57 to 67 GHz with a fixed IF of 5.3 GHz. The corresponding LO suppression was better than 34 dB with 8 dBm of LO power. The IR mixer achieved better than 19 dB of IR ratio and better than 36 dB of LO suppression for an RF frequency from 57 to 66 GHz. The corresponding conversion loss varies from 13 to 16 dB. The measured 1-dB compression point of the IR mixer was at a--13-dBm output power level and the third-order intercept point was at a 4-dBm level. Index Terms--Baluns, MIMICs, resistive mixers.

We present a realistic modeling of ballistic electron transport in a hybrid ferromagnetic (FM) two-dimensional electron gas (2DEG) device, consisting of an FM gate on an AlGaAs-GaAs or AlSb-InAs high electron mobility transistor (HEMT) heterostructure. The carriers within the 2DEG are spin-polarized by a combination of magnetic and electrostatic barriers. The magnetic barriers are supplied by a composite FM gate, consisting of two domains made of magnetically hard and soft materials. This gate arrangement breaks the antisymmetry of the fringe B field, and results in a finite spin polarization of the 2DEG current. The B field strength is calculated by considering the pole strength at the gate surfaces and domain boundary, and is significantly weaker than normally assumed. We obtain parameters such as the electrostatic barrier height, Fermi level, and carrier concentration within the 2DEG by a finite-element Poisson calculation, which is self-consistent with the Fermi-Dirac distribution. We calculate the transmission probability and conductance through the 2DEG from these parameter values, assuming a single particle effective mass Hamiltonian and purely ballistic transport. We show that the spin polarization ratio [P.sub.G] is extremely sensitive to the gate bias and HEMT doping concentration. However, the maximum [P.sub.G] is extremely low for AIGaAs-GaAs (0.003%) and even for AlSb-InAs (0.12%) devices, despite a large Lande g factor. These values are many orders of magnitude smaller than previous predictions of close to 100% polarization, obtained by using simpler models. Index Terms--Ballistic transport, ferromagnetic 2DEG, finite-element method, spin polarization.

The effect of noise figure of different AlGaN/GaN high electron-mobility transistor (HEMT) epitaxy structures is reported. The addition of a thin AIN layer between the barrier and channel gives better performance at biasings other than the best for minimum noise figure. However, varying Al composition in the HEMT barrier does not change the noise performance, contrary to a 2003 study by Lu et al. The measurements are checked with both the Pospieszalski and van der Ziel (Pucel) models. The models are used on six different samples, helping to reinforce the measurements and showing the strengths and weaknesses of each. Index Terms--AlGaN, GaN, high electron-mobility transistor (HEMT), noise figure, Pospieszalski, Pucel, van der Ziei.

Phototransistors based on InP high electron-mobility transistors (HEMTs) are investigated for millimeter-wave radio-on-fiber system applications. By clarifying the photodetection mechanism in InP HEMTs, the phototransistor internal gain is determined. We present their use as millimeter-wave harmonic optoelectronic mixers and characterize them at the 60-GHz band. In order to evaluate the InP HEMT optoelectronic mixer performance, internal conversion gain is introduced and a maximum of 17 dB is obtained for 60-GHz harmonic optoelectronic up-conversion. Utilizing them, we construct a 60-GHz radio-on-fiber system and demonstrate 622-Mb/s data transmission over 30-km single-mode fiber and 3-m free space at 60-GHz band. Index Terms--High electron-mobility transistor (HEMT), optically controlled microwave device, optoelectronic mixer, photodetector, phototransistor.

We review the design and experimental results of three new AlGaN/GaN high electron-mobility transistor monolithic microwave integrated circuits: a voltage-controlled oscillator (VCO), a single-pole-double-throw switch (SPDT), and a resistive field-effect transistor mixer. The VCO exhibits frequency range between 8.5-9.5 GHz with maximum output power of 35 dBm (at [V.sub.ds] = 30 V) across a 50-[ohm] load. The L/S band SPDT switch at 0.9, 1.8, and 2.1 GHz was measured to have 0.87-, 0.96-, 1-dB insertion loss and 46-, 42-, and 41-dB isolation, respectively. The switch also shows linear performance for the power levels up to 1 W in the insertion mode. A singly ended X-band resistive mixer has exhibited very low intermodulation, less than -60 dBc for the second and third harmonics of the IF at the RF power level of 10 dBm, and high power handling, [P.sub.1 dB] is estimated to be at least 1 W, with the conversion loss of 17 dB. Index Terms--AlGaN/GaN high electron-mobility transistor (HEMT), field-effect transistor (FET) mixer, monolithic microwave integrated circuit (MMIC), switch, voltage-controlled oscillator (VCO).

Undoped AIGaN-GaN power high electron mobility transistors (HEMTs) on sapphire substrate with 470-V breakdown voltage were fabricated and demonstrated as a main switching device for a high-voltage dc-dc converter. The results show the possibilities of AIGaN-GaN power HEMTs on sapphire substrate for future switching power devices.

We present a high-directivity photonic emitter with a high-gain antenna and waveguide-output photodiode module (WG-PM) for extending the transmission distance of a wireless link that uses a 120-GHz millimeter wave. The module employs a uni-traveling-carrier photodiode, broad-band high electron-mobility transistor (HEMT) amplifier, and planar-circuit-to-waveguide transition substrate. The maximum output power of the WG-PM is 8 dBm at a frequency of 120 GHz, and it has a 3-dB bandwidth of over 16 GHz. The wireless link with the high-directivity photonic emitter achieved 10-Gbit/s wireless data transmission, and using a high-gain Gaussian optic lens antenna and an HEMT amplifier reduced the input optical power necessary for error-free transmission. The transmission characteristics of the link showed that its transmission distance can be extended to over 100 m. Index Terms--Broad-band communication, high electron-mobility transistor (HEMT), millimeter-wave (MMW) radio communication, photodiodes (PDs).

This paper describes the design of millimeter-wave wide-band monolithic GaAs passive high electron-mobility transistor (HEMT) switches using the traveling-wave concept. This type of switch combined the off-state shunt transistors and series microstrip lines to form an artificial transmission line with 50-[ohm] characteristic impedance. A 15-80-GHz single-pole double-throw (SPDT) switch in conjunction with quarter-wavelength impedance transformers demonstrates an insertion loss of less than 3.6 dB and an isolation of better than 25 dB. Another type of wide-band switch was designed by using a series HEMT switch to replace the quarter-wavelength transformer, and the operating band can be extended to dc. With this scheme, dc-80-GHz single-pole single-throw (SPST) and dc-60-GHz SPDT switches are also developed with compact chip size. From dc to 80 GHz, the insertion loss and isolation of the SPST switch are better than 3 and 24 dB, respectively. The SPDT switch has an insertion loss of better than 3 dB and an isolation of better than 25 dB from dc to 60 GHz. The analysis of circuit characteristics and design procedures are also included. It is concluded that the device periphery can be selected for the desired bandwidth, while the number of transistors is decided to achieve the isolation. Index Terms--High electron-mobility transistor (HEMT), switch, traveling wave.

The static and dynamic characteristics of 50-nm-gate A1INAs delta-doped high-electron mobility transistors (HEMTs) are investigated using a Monte Carlo simulator. The study confirms that the value of the delta-doping must be increased to avoid the reduction of the drain current due to the depletion of the channel by the surface potential.

A 50-Gbit/s InP high electron-mobility transistor (HEMT) chip set of 4:1 multiplexer (MUX) and 1:4 demultiplexer (DMUX) integrated circuits (ICs) with a multiphase clock (MPC) architecture is described. The MPC architecture employs a quarter-rate four-phase clock generated by a toggle flip-flop inside the ICs, which reduces the number of circuit elements and lowers the power consumption. The fabricated 4:1 MUX and 1:4 DMUX ICs exhibited 50-Gbit/s error-free operations for [2.sup.31] - 1 pseudorandom bit sequences with 1.71- and 1.42-W power consumption, respectively. Compared to conventional tree-type 4:1 MUX and 1:4 DMUX ICs using InP HEMTs, the MPC 4:1 MUX and 1:4 DMUX Ics operate at the same operating speed with less than one-third power consumption. Index Terms--4:1 multiplexer (MUX), InP high electron-mobility transistor (HEMT), multiphase clock (MPC), OC-768, 1:4 demultiplexer (DMUX), optical communication systems, STM-256.

A wide-band on-wafer noise-parameter measurement setup has been developed for W-band. The system is based on a cold-source method and uses a simple manual impedance tuner. In addition to noise parameters, S-parameters can be measured with the same setup. Using the developed system, noise parameters of an InP high electron-mobility transistor have been measured and results are shown in the 79-94-GHz frequency band. This is the first comprehensive report of noise-parameter measurements made on active devices at W-band. Index Terms--High electron-mobility transistor (HEMT), noise measurement, noise parameter, on-wafer characterization.

The large-characteristics of GaN-A1(sub x)Ga(sub 1-x)N high-electron mobility transistors (HEMTs) with particular emphasis on intermodulation distortion (IMD) and the third-order intercept point are analyzed. GaN system has the potential for microwave and RF applications at elevated temperatures.

The 1/f channel noise of GaAs based pseudomorphic high electron mobility transistors (PHEMT'S) is studied. Values of access resistance are an important parameter to describe noise behavior.

An algorithm is presented that allows for noniterative extraction of the parameters of the Pucel and Pospieszalski FET noise models directly from noise-figure measurements. Since the goal is to minimize the number of source-pull measurements, the number of different source admittances required as a minimum to determine the model parameters reliably is investigated. It turns out that, in the case of the Pospieszalski model, 50-[ohm] measurements are sufficient, while in case of the Pucel model, three additional source impedances have to be taken into account. The results are verified by investigating MESFET and pseudomorphic high electron-mobility transistor devices. Index Terms--Equivalent circuits, MESFETs, MODFETs, noise measurement, semiconductor device modeling, semiconductor device noise.

Time-resolved charge-collection measurements performed on AISb/InAs/GaSb resonant interband tunneling diodes (RITDs) with pulsed laser excitation exhibit complex behavior as a function of the device operating point. A model considering conventional charge-collection principles in combination with transient band-bending effects is proposed to describe the experimental results. In the proposed model, a transient distortion of the band structure of the device (transient band bending) induced by holes trapped in the GaSb valence band well modulates the dc current through the RITD. The manner in which this transient modulation is manifested in the experimental observable depends sensitively on the operating point of the device, giving rise to qualitatively different temporal signatures under different dc bias conditions. Index Terms--Charge collection, high electron mobility transistor (HEMT), monostable-bistable transition logic element (MOBILE), resonant interband tunneling diode (RITD), resonant tunneling diode (RTD), single-event effects (SEEs), single-event upset (SEU), transient band bending.

The variation of high electron-mobility transistor (HEMT) large-signal behavior with a change in operating condition is examined with a view to understanding the dynamics involved and developing a modeling strategy. The observed variation exhibits the dynamics of thermal, impact ionization, and trapping effects. A novel measurement of drain characteristic transients gives time-evolution information that clearly shows these as separate quantifiable phenomena with significant dependence on initial operating conditions. A drain-current model that describes high-frequency characteristics with pinchoff, gain, and drain feedback parameters is adapted to describe the variation of the characteristics with changing operating conditions. The results reported give insight and grounding for simulation of HEMT circuits. Index Terms--HEMTs, high-speed devices, impact ionization, kink effect, pulsed characterization.

Breakdown enhancement potential of the field plate (FP) technique is investigated, in a context of AlGaN/GaN power high electron mobility transistors (HEMT). Higher breakdown enhancement is possible using a higher insulator dialectric constant. The methodology used here can be extended to other FP structures in other lateral field-effect transistors (FET).

Research into the design and fabrication of a pseudomorphic high electron mobility transistor is presented. The performance of the device at temperatures from 300 to 450K and gate-to-drain voltage are analysed.

Research describing the characteristics of microcrystalline silicon thin films is presented. In particular transport and structural properties for different thicknesses are investigated.

The modeling and measurements of metamorphic high-electron mobility transistors are presented. Enhancement mode Al0.66In0.34As/Ga0.67In0.33As structures are used.

A novel gallium nitride-based high electron mobility transistor power amplifier design is presented that uses an artificial neural network modeling technique.

The fabrication of a recessed gate high electron mobility transistor is described.

Research into the power density of AlGaN/GaN HEMTs is presented.

A new study investigates the high frequency noise characteristics of AlGaN/GaN HEMTs.

The fabrication of high electron mobility transistors using undoped AlGaN/GaN structures and the induction of a two-dimensional electron gas are described.

The fabrication of high electron mobility transistors using undoped AlGaN/GaN structures and the induction of a two-dimensional electron gas is described.

A new study uses low energy electron-excited nanoscale luminescence spectroscopy to identify the AlGaN deep level defects in AlGaN/GaN high electron mobility transistor device structures.

The fabrication and performance of AlGaN/GaN high electron mobility transistors on silicon substrates is investigated using organometallic vapor phase epitaxy.

The small-signal, dc, and microwave power output characteristics of GaN-based field-effect transistors are presented.

The fabrication and performance of AlGaN/GaN high electron mobility transistors on silicon substrates isn investigated using organometallic vapor phase epitaxy.

The effects of nonlinear electronic transport, particularly real space transfer, on high electron mobility transistors, are examined.

Surface photovoltage spectroscopy and numerical simulations were used to characterize pseudomorphic high electron mobility transistor structures.

Surface passivation was successfully achieved of wide recess InGaP/InGaAs/GaAs pseudomorphic high electron mobility transistors, with ultrathin GaS film.

A method of diagnosing the physical mechanisms that limit manufacturing uniformity of millimeter-wave power InAIAs/InGaAs high electron mobility transistors on InP is presented.

A model for the kink effect in InA1As/InGaAs HEMTs is presented.

An output power drift mechanism is proposed under rf overdrive of pseudomorphic high electron mobility transistors.

A new study examines the effect of doping level and thickness on carrier transport in high-power AlGaN/GaN high electron mobility transistor structures.

AlGaAs/InGaAs pseudomorphic hot-electron-mobility transistors (HEMTs) have been investigated. Hot carrier transport phenomena have been analyzed. A dominant contribution in the electroluminescence spectra of pseudomorphic HEMTs from electron-hole recombination is confirmed. A composite peak from recombination of cold carriers has been identified and analyzed using a high-resolution monochromator. Evidence of recombination of the AlGaAs layers at high electric field exists. That shows real space transfer of holes and electrons.