Performance Of MESFETs Research Articles

Temperature Dependent Small- and Large-Signal Performance of 4H-SiC MESFET's

Temperature Dependent Small- and Large-Signal Performance of 4H-SiC MESFET's

Noise modeling in MESFET and HEMT mixers using a uniform noisy line model

The aim of this paper is to present a noise model which predicts the noise performance of MESFET and HEMT mixers. The conversion and noise correlation matrices of a FET mixer are calculated using a uniform nonlinear noisy active line concept to describe the FET. This calculation is based on a perturbation analysis of the large-signal noiseless steady state, making it a microscopic nonlinear noise model. This method is applied to the case of a hot HEMT gate mixer and we show that the theoretical results are in agreement with experimental data.

Neutron irradiation of cold GaAs devices and circuits made with an ion-implanted monolithic process

We have irradiated with neutrons from SARA facility (Grenoble) four versions of cryogenic GaAs monolithic preamplifiers and one MESFET at 87 K. The preamplifiers were designed to readout the ionization signal from the LAr electromagnetic calorimeter of ATLAS experiment. In this paper, data on modification of preamplifier transfer function and degradation of noise performance with irradiation are presented. New preamplifiers (M- and D-versions) exhibited better resistance to irradiation than old C3 version, thanks to a better design of second stage. DC performance of MESFET has been well characterized before and after irradiation. Due to effects of carrier removal and mobility degradation, pinch-off voltage V p and maximum drain current I dss dropped by factor 2.1 and 7.4, respectively, while the transconductance at standing current I d = 8 mA did not change after a fluence of about 13×10 14 neutrons cm 2 (1 MeV equivalent).

RF and 1/f noise investigations on MESFETs and circuits transplanted by epitaxial lift off

In this paper, we present the results of RF and noise measurements of MESFETs transplanted by epitaxial lift off (ELO). ELO is a technology by which epitaxially grown layers are lifted off from their growth substrate and subsequently reattached to a new host substrate. In the experiments described here a 800 mm thick GaAs film containing MESFETs or complete microwave circuits is transplanted onto semi-insulating InP. Gate leakage current, RF characteristics, and noise performance of MESFETs and GaAs circuits are compared before and after ELO. Special attention was given to low-frequency (1/f) noise, 1/f noise is believed to be caused by surface as well as bulk effects. An increase in 1/f noise could have been predicted since a new surface is exposed during the transplantation process. The mechanical stress during the transplantation could cause crystal damage creating additional traps which could also result in an increase in 1/f noise.

MESFET performance and limitations of optimized GaAs strained buffer layer grown on InP by molecular beam epitaxy

The effects of the thickness of the GaAs strained buffer layer on the electrical performance of GaAs field effect transistors are demonstrated. The GaAs MESFET has been fabricated on GaAs/InP epitaxial material grown by molecular beam epitaxy. From experimental results a minimum thickness of the strained buffer layer appears to be needed to compensate the effect of misfit dislocation due to lattice mismatch between the GaAs and InP substrate. The minimum required thickness amounts to 2 μm. The electron mobility and transconductance behavior demonstrate the effects of thickness of the strained buffer layer.

Influence of the gate leakage current on the noise performance of MESFETs and MODFETs

In this paper, the influence of the gate leakage current on the noise performance of MESFETs and MODFETs is investigated. Both a simple analytical model and a more realistic numerical model have been developed. It is shown that the noise performance is strongly dependent on the gate leakage current value, especially at low frequency. The theoretical results are discussed and compared with experimental ones.

RF performance of SiC MESFET's on high resistivity substrates

State-of-the art SiC MESFET's showing a record high f/sub max/ of 26 GHz and RF gain of 8.5 dB at 10 GHz are described in this paper. These results were obtained by using high-resistivity SiC substrates for the first time to minimize substrate parasitics. The fabrication and characterization of these devices are discussed. >

Microwave performance of GaN MESFETs

GaN MESFETs have been fabricated with a 0.25 mu m thick channel on a high resistivity GaN layer grown by metal organic vapour phase epitaxy. These devices have a transconductance of 20 mS/mm. For a 0.7 mu m gate length device, the measured f/sub T/ and f/sub max/ were 8 and 17 GHz, respectively.

Device performance of submicrometre MESFETs with LTG passivation

The device characteristics of a submicrometre GaAs MESFET with low-temperature-grown GaAs passivation are reported. The fabricated device has a high gate-drain breakdown voltage of over 20V with a maximum drain current of 340 mA/mm and a transconductance of 200 mS/mm. Microwave measurement of the device yields a cutoff frequency of 32 GHz, and an unusually high maximum frequency of oscillation of 110 GHz. These combined characteristics demonstrate the potential of the device as a viable power amplifier in the millimetre-wave frequency range

Investigation of low temperature (LT) layers of GaAs grown by MBE: comparison of MESFET and HEMT performance

GaAs buffer layers grown on GaAs (100) by MBE and modulated flux MBE (MF MBE) were investigated using substrate temperatures between 200 and 600°C, growth rate 1 μm/h and equivalent pressure ratio P As4 P Ga =7−17 . The growth process was investigated by RHEED observation, crystallinity of samples by electron channelling pattern (ECP) and surface morphology by scanning electron microscopy (SEM). LT layers have been incorporated as buffer layers in MESFET and HEMT structures in order to eliminate sidegating, kink effect and hysteresis in the I-V characteristics. Comparison has been made between MESFETs and HEMTs incorporating LT buffer layers, SL buffer layers and p-AlGaAs buffer layers.

Silicon carbide microwave MESFET's

Summary form only given. The authors describe record-setting 5-GHz SiC MESFET performance and the effects of device design on achieving these results. Bulk growth of 6H-SiC was performed using a physical vapor transport process, and the resultant undoped single-crystal boules were sliced and polished to generate 1-in-diameter wafers. These wafers were then used as substrates for the chemical vapor deposition of doped silicon carbide active layers. Wafers contained 24 chips, each consisting of an array of MESFETs having systematically varied geometry. A sample DC characteristic from a 320- mu m periphery MESFET showed a knee voltage of 8 V, a transconductance of 20 mS/mm, a maximum channel current of 210 mA/mm, and a gate-to-drain breakdown voltage of 100 V. Automated RF probing was used to obtain wafer maps of small signal gain, F/sub T/, and F/sub max/, revealing an excellent transistor yield of 87%. The highest-gain MESFETs in the array developed 12 dB of gain at 2 GHz with a cutoff frequency of 5 GHz. >

Analytical model of low-frequency diffusion noise in GaAs MESFETs

A simple analytical formula for the low-frequency noise (below 10 kHz) in GaAs MESFETs is derived. This unipolar model describes noise generated in the semi-insulating substrate and involves diffusion, drift, and generation-recombination due to deep-level traps. The derived noise spectrum is diffusion-like and rolls off as f/sup -3/2/ at the high-frequency limit. The results are formally identical to the conventional diffusion/drift noise spectrum except the diffusion/drift constants are replaced by their reduced counterparts. Good qualitative agreement with experiments has been obtained for temperature, length, and field dependences. The derived spectrum can be computed quickly and is suitable for use in circuit simulation of low-frequency performance of MESFETs. >

Heterojunction ion-implanted FETs (HIFETs)

The authors report the enhanced microwave performance of ion-implanted MESFETs fabricated on graded GaAs-AlGaAs heterostructures. Since low-noise MESFETs are typically biased at a low drain current, optimum low-noise operation requires high f/sub 1/ at low drain currents. f/sub t/ values reported in the literature are generally measured close to I/sub dss/. This 0.5- mu m gate heterojunction ion-implanted FET (HIFET) exhibits enhanced microwave performance, especially at low drain current, when compared to conventional ion-implanted GaAs MESFETs. At 20% of I/sub dss/, the current gain cutoff frequency f/sub t/ is 40 GHz, which increases to 47 GHz at 50% of I/sub dss/. At 100% of I/sub dss/, the f/sub t/ is 41 GHz. The maximum stable gain at 25 GHz of the HIFET is also 4 dB higher than that of the conventional MESFET.

Enhanced microwave performance of ion-implanted MESFET with graded GaAs/AlGaAs heterojunctions

Ion-implanted MESFETs have been fabricated on an inverted GaAs/AlGaAs heterostructure. The aluminium concentration in the AlGaAs is graded from 0% at the substrate to 30% at the heterointerface. A maximum extrinsic transconductance of 410 mS/mm is achieved with 0.5 µm gate devices. This heterojunction ion-implanted FET (HIFET) also exhibits enhanced microwave performance, especially at low drain current, when compared to conventional ionimplanted GaAs MESFETs. At 20% of Idss the current gain cutoff frequency ftis 40 GHz, which increases up to a maximum value of 47 GHz as the drain current rises. These characteristics of high ft and high gain at low current are advantageous for low-noise applications.

Improvement of GaAs MESFET performance using surface p-layer doping (SPD) technique

The development of a surface p-layer doping (SPD) technique to improve GaAs MESFET performance is presented. Very shallow p-type doping into the gate-drain and gate-source regions is used to improve the output conductance of the device. It is found that the threshold voltage is independent of the SPD dose. The transconductance degrades significantly as the p doping (Be, 10 keV) increases above 3*10/sup 12//cm/sup 2/. However, the output conductance and subthreshold current are improved with higher SPD dose. The gate-source reverse breakdown voltage is improved by about 90%, and the parasitic resistance increases by about 30% with an SPD of 5*10/sup 12//cm/sup 2/. >

High-current pulse-doped GaInAs MESFET

We report the DC and microwave performance of pulse-doped GaInAs power MESFETs. For a 0.7μm gate-length device, a maximum drain-current density of 870mA/mm and a peak transconductance of 325mS/mm were measured. A maximum stable gain of 11.7dB at 26 GHz, and an extrapolated ft, of 33 GHz were obtained. These values are the highest reported for MESFETs having gates as long as 0.7 μm.

Noise modeling and measurement techniques (HEMTs)

The high electron mobility transistor's (HEMT's) noise behavior is presented from theoretical and experimental points of view. The general method used in the high-frequency noise analysis is described and the different approximations commonly used in the derivation of the noise parameter expressions are discussed. A comparison between the noise performance of both MESFETs and HEMTs is carried out. The measurement techniques providing the noise figure and the other noise parameters are then described and compared.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Properties of Patterned Gallium Arsenide on Silicon

AbstractThe growth of GaAs on Si by MBE through openings in an oxide or nitride represents a convenient means for achieving monolithic GaAs/Si integration. We have examined a number of the materials growth and processing issues that must be resolved in order to achieve this goal. Some of the specific areas that have been investigated are (a) the effect of trench etching on the morphology of the patterned GaAs; (b) the dependence of patterned feature size on Hall mobility in both as-grown and postgrowth annealed samples; (c) the effect of annealing on the defect structure in the transition region from single crystal GaAs to polycrystalline growth; (d) the dependence of GaAs MESFET performance on proximity to the polycrystal transition; and (e) the performance of Si MOS devices following the GaAs MBE growth. Specific growth and processing issues concerning the integration of GaAs and Si device functions have also been examined.

External stress effect on GaAs MESFET Characteristics

An experimental investigation has been carried out for clarifying the external mechanical stress effect on GaAs MESFET performance. The stress was induced by bending wafers. It was found that threshold voltage varied linearly with the applied stress. In the case of refractory-gate n+ self-aligned FET's (L G = 1 µm), the magnitude was about 10 mV for 2 × 108-dyn/cm2stress change. The threshold voltage shift direction was opposite for [011]- and [011]-oriented FET's. These results were found to be caused by a change in refractory-gate electrode stress which produces piezoelectrical charge densities in the GaAs substrate.

Prediction of Wide-Band Power Performance of MESFET Distributed Amplifiers Using the Volterra Series Representation

The power performance of a four-section MESFET distributed amplifier is predicted over the frequency range 2-8 GHz. The nonlinear model of the MESFET used has three nonlinear elements: g/sub d/, and C/sub gs/, which are represented by power series up to the third order. The analysis employs the Volterra series representation up to the third order. Experimental verification is first made on a 0.5x400-µm medium-power MESFET device to confirm the validity of the nonlinear model used in the analysis. The agreement between predicted and measured output power at 1-dB gain compression is within +-0.5 dBm across the 2-16 GHz band. A four-section distributed amplifier was then built with four 0.5x400-µm MESFET's. The agreement between predicted and measured output power at 1-dB gain compression of this amplifier is within +-0.7 dBm across the 2-8-GHz band. The measured output power at 1-dB gain compression is (22+-1) dBm across the 2-8-GHz band.