M. Feng

Does the two‐dimensional electron gas effect contribute to high‐frequency and high‐speed performance of field‐effect transistors?

We present experimental evidence that current gain cutoff frequency (ft) values equal to or greater than those achieved with high electron mobility transistors (HEMTs) and pseudomorphic HEMTs can also be achieved by ion‐implanted GaAs and InGaAs metal‐semiconductor field‐effect transistors. These measured ft results clearly suggest that the average electron velocity under the gate is determined primarily by the high‐field electron velocity rather than the low‐field electron mobility. Hence, we conclude that the transport properties of the two‐dimensional electron gas in HEMTs and pseudomorphic HEMTs do not make a significant contribution to the high‐frequency and high‐speed performance of these devices.

Half-micrometer gate-length ion-implanted GaAs MESFET with 0.8-dB noise figure at 16 GHz

Ion-implanted GaAs MESFETs with half-micrometer gate length have been fabricated on 3-in-diameter GaAs substrates. At 16 GHz, a minimum noise figure of 0.8 dB with an associated gain of 6.3 dB has been measured. This noise figure is believed to be the lowest ever reported for 0.5- and 0.25- mu m ion-implanted MESFETs, and is comparable to that for 0.25- mu m HEMTs at this frequency. By using the Fukui equation and the fitted equivalent circuit model, a K/sub f/ factor of 1.4 has been obtained. These results clearly demonstrate the potential of ion-implanted MESFET technology for K-band low-noise integrated circuit applications.<<ETX>>

High-performance millimeter-wave ion-implanted GaAs MESFETs

GaAs MESFETs (metal-epitaxial-semiconductor-field-effect transistors) with ion-implanted active channels have been fabricated on 3-in-diameter GaAs substrates which demonstrate device performance comparable with that of AlGaAs/InGaAs pseudomorphic HEMT (high-electron-mobility transistor) devices. Implanted MESFETs with 0.5- mu m gate lengths exhibit an extrinsic transconductance of 350 mS/mm. From S-parameter measurements, a current-gain cutoff frequency f/sub 1/ of 48 GHz and a maximum-available-gain cutoff frequency f/sub max/ greater than 100 GHz are achieved. These results clearly demonstrate the suitability of ion-implanted MESFET technology for millimeter-wave discrete device, high-density digital, and monolithic microwave and millimeter-wave IC applications.<<ETX>>

MMIC phase shifters and amplifiers for millimeter-wavelength active arrays

The development of MMIC (monolithic microwave integrated circuit) phase shifters and amplifiers at 20 and 44 GHz for application in space-based active antenna arrays is described. Radio frequency probing to characterize the active elements at these frequencies is shown to provide a good basis for the MMIC design. Measured performance results are presented for a 44-GHz phase-shifter switching element, all 16 states of a 4-b 20-GHz MMIC phase shifter, a 180 degrees 44-GHz phase shifter, and a three-stage 20-GHz amplifier.<<ETX>>

Quarter-micrometer gate ion-implanted GaAs MESFET's with an f/sub 1/ of 126 GHz

The fabrication and characterization of a 0.25- mu m-gate, ion-implanted GaAs MESFET with a maximum current-gain cutoff frequency f/sub t/ of 126 GHz is reported. Extrapolation of current gains from bias-dependent S-parameters at 70-100% of I/sub dss/ yields f/sub 1/s of 108-126 GHz. It is projected that an f/sub 1/ of 320 GHz is achievable with 0.1- mu m-gate GaAs MESFETs. This demonstration of f/sub 1/s over 100 GHz with practical 0.25- mu m gate length substantially advances the high-frequency operation limits of short-gate GaAs MESFETs.<<ETX>>

W-band oscillator using ion-implanted InGaAs MESFETs

A fundamental FET oscillator that operates at 92.3 GHz with an output power of 14 mW and with V/sub DS/=3.9 volts is reported. The efficiency is 11% at this point. The data are referenced to the waveguide output port with no corrections for the transition or fixture loss. By tuning the input waveguide short, the device oscillation frequency could be tuned from approximately 91-93 GHz. Maximum power was attained at 92.3 GHz. The output spectrum of this oscillator shows the sideband noise to be approximately -70 dBc/Hz for all offset frequency of 15 kHz. This is comparable to commercial W-band Gunn oscillators.<<ETX>>

0.25- mu m gate millimeter-wave ion-implanted GaAs MESFETs

Quarter-micrometer gated ion-implanted GaAs MESFETs which demonstrate device performance comparable to AlGaAs/InGaAs pseudomorphic HEMTs (high-electron mobility transistors) have been successfully fabricated on 3-in-diameter GaAs substrates. The MESFETs show a peak extrinsic transconductance of 480 mS/mm with a high channel current of 720 mA/mm. From S-parameter measurements, the MESFETs show a peak current-gain cutoff frequency f/sub t/ of 68 GHz with an average f/sub t/ of 62 GHz across the wafer. The 0.25- mu m gate MESFETs also exhibit a maximum-available-gain cutoff frequency f/sub t/ greater than 100 GHz. These results are the first demonstration of potential volume production of high-performance ion-implanted MESFETs for millimeter-wave application.<<ETX>>

Ultrahigh-frequency performance of submicrometer-gate ion-implanted GaAs MESFETs

A study of the high-frequency performance of short-gate ion-implanted GaAs MESFETs with gate lengths of 0.3 and 0.5 mu m is discussed. Excellent DC and microwave performance have been achieved with an emphasis on the reduction of effective gate length during device fabrication. From f/sub t/ of 83 and 48 GHz for 0.3-0.5- mu m gate devices, respectively, an electron velocity of 1.5*10/sup 7/ cm/s is estimated. An f/sub t/ of 240 GHz is also projected for a 0.1- mu m-gate GaAs MESFET. These experimental results are believed to be comparable to those of the best HEMTs (high-electron-mobility transistors) reported and higher than those generally accepted for MESFETs.<<ETX>>

GaAs MESFET's made by ion implantation into MOCVD Buffer layers

Low-noise GaAs metal-semiconductor field-effect transistors (MESFETs) have been made using ion-implanted metal organic chemical vapor deposition (MOCVD) buffer layers. A noise figure of 1.46 dB with 10.20 associated gain has been achieved at 12 GHz for a 0.5-µm gatelength by 300-µm gatewidth FET device. This result demonstrates that excellent GaAs LNFETs can be made by ion implantation into MOCVD buffer layers, comparable to the best results obtained from similar devices made by AsCl3vapor-phase epitaxy and molecular-beam epitaxy.

Millimeter-wave ion-implanted graded In/sub x/Ga/sub 1-x/As MESFETs grown by MOCVD

The authors present the fabrication and characterization of ion-implanted graded In/sub x/Ga/sub 1-x/As/GaAs MESFETs. The In/sub x/Ga/sub 1-x/As layers are grown on GaAs substrates by MOCVD (metal-organic chemical vapor deposition) with InAs concentration graded from 15% at the substrate to 0% at the surface. 0.5- mu m gate MESFETs are fabricated on these wafers using silicon ion implantation. In addition to improved Schottky contact, the graded In/sub x/Ga/sub 1-x/As MESFET achieves maximum extrinsic transconductance of 460 mS/mm and a current-gain cutoff frequency f/sub t/ of 61 GHz, which is the highest ever reported for a 0.5- mu m gate MESFET. In comparison, In/sub 0.1/Ga/sub 0.9/As MESFETs fabricated with the same processing technique show an f/sub t/ of 55 GHz.<<ETX>>