M.R.S. Taylor

A high performance, high yield, dry-etched, pseudomorphic HEMT for W-band use

A GaAs pseudomorphic HEMT process has been optimised for high performance and yield at W-band. Several key nano-fabrication techniques are explored for performance, manufacturability and process sensitivity. The molecular beam epitaxially grown pHEMT layer is optimised for reduced short channel effects, high transconductance (690 mS/mm) and reliability. Electron-beam lithography produces ultra short T-gates with high reproducibility. Selective reactive ion etching enables both the depth and width of the gate recess to be accurately controlled. 0.2 /spl mu/m pHEMTs with two 50 /spl mu/m gate fingers exhibit average values for f/sub T/ and f/sub max/ of 121 and 157 GHz with low standard deviations of 4.6 and 2.9 GHz respectively.<<ETX>>

94 and 150 GHz coplanar waveguide MMIC amplifiers realized using InP technology

We report the design, fabrication and measurement of a three stage W-band amplifier with up to 22 dB gain at 94 GHz and a single stage D-band amplifier with 5 dB gain at 150 GHz. Circuits were designed and fabricated in coplanar waveguide technology using a 0.121 /spl mu/m T-gate lattice matched InP HEMT technology.

Fabrication and high frequency characterisation of GaAs MESFETs with gate lengths down to 30 nm

Abstract This paper describes a process to fabricate GaAs MESFETs with gate lengths in the range 270 to 30nm suitable for high frequency characterisation. Electron beam lithography was used to define all device levels on layers grown by molecular beam epitaxy (MBE). Processing included a dry etched mesa for isolation, low temperature annealed ohmic contacts, and a gate recess etch containing a wetting agent to improve etching uniformity. The MESFETs were characterised at DC and high frequency. 30nm gate length devices exhibited DC transconductances of up to 710mS/mm and unity gain cut off frequencies of up to 150GHz extrapolated at 6dB/octave from 20GHz.

150GHz Coplanar Waveguide MMIC Amplifier

We report the design, fabrication and measurement of a single stage D-Band amplifier with 3-4dB gain at 150GHz. In addition a three stage D-Band amplifier with 7.5dB gain at 153GHz is reported. Circuits were designed and fabricated in coplanar Waveguide technology using a 0.12¿m T-gate lattice matched InP HEMT technology.

W-Band Performance of Coplanar Waveguide on Thinned Substrates

We report on the measured mmwave (67-110GHz) performance of Coplanar Waveguide components on GaAs substrates as a function of substrate thickness, for calibration and circuit applications in W-band and D-band. W-band measurements show improved mmwave performance of transmission lines and short circuit elements on thinner substrates.

Very high frequency performance of nanometre scale GaAs MESFETs

Summary form only given. GaAs MESFETs with gate lengths from 250 to 30 nm were fabricated and characterized at microwave frequencies. The MESFETs, fabricated on MBE (molecular beam epitaxy) grown layers, were optimized, as far as possible, to reduce short-channel effects. It was found that the inverse proportionality of the gate length with f/sub T/ does not hold for sub-100-nm gate-length GaAs MESFETs. In addition, deviation from the simple mod h/sub 21/ mod versus frequency relationship was observed as the gate length was reduced to less than 100 nm. >

Fabrication and Simulation of 0.1 μm Pseudomorphic HEMTs

When the gate length of the pseudomorphic HEMTs (PsHEMTs) approaches 0.1 μm, short channel effects become limiting factor for the device performance, leading to a large negative threshold voltage shift, increase in the output conductance, degradation and subthreshold slope reduction. Most of the authors attribute the short-channel effects in HEMTs mainly to the de-confinement of the channel carriers [1]. The proposed solution is enhancement of the confining step potential below die channel together with a reduction of the distance between the gate and the channel in order to preserve a large aspect ratio.