Gate recess engineering of pseudomorphic In0.30GaAs/GaAs HEMTs

The authors report how the performance of 0.12 μm GaAs pHEMTs is improved by controlling both the gate recess width, using selective dry etching, and the gate position in the source drain gap, using electron beam lithography. pHEMTs with a transconductance of 600 mS/mm, off state breakdown voltages >2 V, fτ of 120 GHz, f max of 180 GHz and MAG of 13.5 dB at 60 GHz are reported

Reduced short channel effects in selectively dry gate recessed P-doped buffered pseudomorphic HEMTs

We report both on the design by numerical simulation of pseudomorphic HEMTs with p-doped and undoped buffer layers and on their fabrication. We report that the p-buffer helps to reduce short channel effects in scaled 100 nm devices. To the authors' knowledge this is the first time that the application of p-doped buffer layers to HEMTs has been demonstrated

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

Low-frequency noise of selectively dry-etch gate-recessed GaAs MESFETs

The authors report the input referred low-frequency noise (2-100 kHz) spectra of 0.2 mu m-gate-length GaAs MESFETs which were gate-recess-etched using a selective Freon 12 based dry-etching process. For comparison, the noise spectra of nonselective wet-chemical, ammonia-based gate-recess-etched devices are also presented. Little change in low-frequency noise performance is observed for devices dry-etched for 30-50 s, demonstrating the latitude of the dry-etch process. Additionally, the input referred noise of the wet-etched devices was greater than that of 30, 40 and 50 s dry-etched devices, suggesting that the dry-etching process may passivate traps contributing to the low-frequency noise component of the MESFETs.<

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

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

W-band on wafer measurement of active and passive devices

In this paper we have presented a study of the effect of back-thinning standard CPW wafers and the influence on measured W-band performance. Improvements in measured insertion loss and substrate cross-talk have been observed, and a study of the effect of a quartz spacer layer has been made. Additionally, the improvement in measured performance of active devices after wafer thinning has also been shown, and further progress is expected in this area