G. W. Wang

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>>

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>>

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>>

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>>

Heteroepitaxial In0.1Ga0.9As metal‐semiconductor field‐effect transistors fabricated on GaAs and Si substrates

We present a comparison of device characteristics for In0.1 Ga0.9 As metal‐semiconductor field‐effect transistors (MESFETs) fabricated on GaAs and silicon substrates. The In0.1Ga0.9As layers are heteroepitaxially grown on GaAs and silicon substrates by metalorganic chemical vapor deposition. 0.5 μm gate devices fabricated on the GaAs substrate show a maximum extrinsic transconductance of 450 mS/mm and a current‐gain cutoff frequency ft of 55 GHz. Despite the large lattice mismatch, the In0.1 Ga0.9 As MESFETs fabricated on the silicon substrate show a comparable ft of 52 GHz with a lower gain.

Ion-implanted In0.1Ga0.9As metal-semiconductor field-effect transistors on GaAs (100) substrates

Ion‐implanted In0.1Ga0.9As metal‐semiconductor field‐effect transistors (MESFETs) have been fabricated on 3 in. GaAs (100) substrates. The structure comprises an undoped InGaAs epitaxially layer grown directly on a GaAs (100) substrate by the metalorganic chemical vapor deposition (MOCVD) technique. Si+28 is ion implanted into the InGaAs layer to form an active channel layer. MESFETs with 100 μm gate width and 0.5 μm gate length are fabricated using standard process techniques. The best device shows a maximum transconductance of 426 mS/mm. From S‐parameter measurements, the current‐gain cutoff frequency ft is 37 GHz and the maximum available gain cutoff frequency fmax is 85 GHz. These results are comparable to InGaAs MESFETs grown by MBE.

44 GHz hybrid low noise amplifiers using ion-implanted In/sub x/Ga/sub 1-x/As MESFETs

Hybrid low-noise amplifiers using ion-implanted In/sub x/Ga/sub 1-x/As MESFETs with 0.25- mu m T-gates have been developed at 44 GHz. The hybrid two-stage amplifier using these ion-implanted In/sub x/Ga/sub 1-x/As MESFETs achieved a noise figure of 3.6 dB with an associated gain of 14.4 dB at 44 GHz. When two of these amplifiers were cascaded, the four-stage amplifier demonstrated a gain of 30.5 dB at 44 GHz and 37 dB at 40 GHz. These results, achieved using low cost ion-implantation techniques, rival the best high-electron-mobility transistor (HEMT) results.<<ETX>>

Graded heterojunction ion-implanted FETs: a combination of heteroepitaxy and ion implantation

FETs fabricated by ion implantation into inverted GaAs-AlGaAs heterostructures grown by MOCVD are discussed. The AlAs fraction in the AlGaAs layer is graded from 0% at the substrate to 30% at the heterointerface. 0.5- mu m gate devices fabricated with the graded heterojunction show two transconductance peaks that are both greater than 420 mS/mm. These devices also exhibit enhanced power gain, especially at low drain current, when compared with conventional ion-implanted GaAs MESFETs. The f/sub t/ of the graded heterojunction device is relatively insensitive to the gate bias. At 20% of I/sub dss/, the measured extrinsic f/sub t/ is 40 GHz, which increases slightly up to 47 and 41 GHz at 50 and 100% of I/sub dss/, respectively. Electron accumulation at the graded GaAs-AlGaAs heterointerface leads to improve device performance at low current bias. >