C.L. Lau

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>>

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>>

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. >

Millimeter-wave power performance of ion-implanted In/sub x/Ga/sub (1-x)/As on GaAs metal semiconductor field-effect transistors

Millimeter-wave power performance achieved by ion-implanted InGaAs-GaAs MESFETs with a gate length of 0.25 mu m is described. When a device with a gate width of 150 mu m was measured at 22 GHz, an output power of 95 mW, a power-added efficiency of 33%, and an associated gain of 7.3 dB were observed. At an output power of 93 mW, a power-added efficiency of 25% and an associated gain of 4 dB were obtained at 44 GHz. When a device with a gate width of 200 mu m was measured at 60 GHz, an output power of 121 mW with 3-dB associated gain and 13% power-added efficiency were observed.<<ETX>>

Mixed technology of ion implantation and heteroepitaxy: ion-implanted In/sub x/Ga/sub 1-x/As/GaAs MESFETs

State-of-the-art FET performance with f/sub t/s of 55 and 61 GHz has been achieved using 0.5- mu m-gate In/sub 0.1/Ga/sub 0.9/As and graded In/sub x/Ga/sub 1-x/As MESFETs, respectively. The material growth and device fabrication are described, and the device characteristics are reported. In comparison to the In/sub 0.1/Ga/sub 0.9/As MESFET, the graded-material MESFET shows a better Schottky gate, which is essential for device performance. This novel InGaAs MESFET is of interest for InGaAs-based circuits that are suitable, among other applications, for long-wavelength fiber-optic communication.<<ETX>>

Heterojunction ion-implanted FETs (HIFETs)

Summary form only given. 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. >