C. Ito

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>>

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>>

A technique for correction of parasitic capacitance on microwave f/sub t/ measurements of MESFET and HEMT devices

A technique for determining the parasitic capacitance attributed to device layout geometry is described. This simple technique requires only on-wafer, cascade probe measurements on devices with varying gate widths. This technique will assist in the optimization of device layout design and in improving modeling performance for microwave and millimeter-wave applications. >

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>>

Full functionality of LSI gate arrays fabricated on 3-in-diameter, MOCVD-grown GaAs-on-silicon substrates

Fully functional, 504-gate arrays have been fabricated on an MOCVD (metalorganic chemical-vapor deposition)-grown, 3-in-diameter, GaAs-on-silicon substrate. Each ECL (emitter-coupled-logic)-compatible gate array consists of an eight-bit adder, a D flip-flop, a 214 divider (with a divide-by-four tap), and a 263-stage inverter string. These circuits represent 90% gate utilization, or approximately 6600 transistors. The wafer-level yield of fully functional gate arrays is 10.7%. This demonstrates total functionality and yield for a digital circuit with LSI-level complexity using MOCVD-grown GaAs-on-silicon material and shows that this material, even with defect densities greater than 108 cm/sup -2/, is viable for high-density LSI circuits.<<ETX>>

Millimeter wave monolithic IC's using direct ion implantation in to GaAs LEC substrates

Millimeter-wave monolithic ICs consisting of two-stage driver amplifiers and 4-bit phase shifters were fabricated by direct ion implantation into 3-inch diameter GaAs LEC (liquid encapsulated Czochralski) substrates. The monolithic two-stage amplifiers with 0.3-micron gate length, ion-implanted GaAs MESFETs achieve a gain of 9.0 to 10.1 dB from 40 to 48 GHz with a gain of 9.5 dB at 44 GHz. In the same frequency range, the input return loss varies from 9.8 to 11.5 dB and output return loss from 6.6 to 9.0 dB. The 4-bit phase shifters exhibit very accurate phase shift within 3 degrees for 0 to 247.5 states and 4-7 degrees for 270 to 337.5 states at 44 GHz. The insertion loss is 9.4 11.1 dB for all 16 states. The authors concentrate on the results of monolithic driver amplifiers and digital phase shifters at Q-band frequencies.<<ETX>>

60-GHz noise performance of ion-implanted In/sub x/Ga/sub 1-x/As MESFET's

The authors report the 60-GHz noise performance of low-noise ion-implanted In/sub x/Ga/sub 1-x/As MESFETs with 0.25 mu m T-shaped gates and amplifiers using these devices. The device noise figure was 2.8 dB with an associated gain of 5.6 dB at 60 GHz. A hybrid two-state amplifier using these ion-implanted In/sub x/Ga/sub 1-x/As MESFETs achieved a noise figure of 4.6 dB with an associated gain of 10.1 dB at 60 GHz. When this amplifier was biased at 100% I/sub dss/, it achieved 11.5-dB gain at 60 GHz. These results, achieved using low-cost ion-implantation techniques, are the best reported noise figures for ion-implanted MESFETs.<<ETX>>

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>>