Low-noise, high-speed Ga/sub 0.47/In/sub 0.53/As/Al/sub 0.48/In/sub 0.52/As 0.1-μm MODFETs and high-gain/bandwidth three-stage amplifier fabricated on GaAs substrate

Abstract

We report on 0.1-/spl mu/m-gate Ga/sub 0.47/In/sub 0.53/As/Al/sub 0.48/In/sub 0.52/As MODFETs fabricated on GaAs substrates by means of the linearly-graded low-temperature buffer-layer (LGLTBL) MBE growth technique. Comparing with control devices on InP substrates we conclude that this is a very promising approach for improved manufacturability with uncompromised performance. GaAs- and InP-substrate MODFETs have a similar combination of maximum current and breakdown voltage. GaAs-substrate MODFETs have lower gate leakage and improved pinchoff. The lower leakage reduces the noise, and on a wafer with low interfacial gate resistance a median minimum noise figure of 0.25 dB at 12 GHz, with 15 dB associated gain, was measured on wafer. High cutoff frequencies are maintained when switching to the GaAs substrate, and the g/sub m/-dispersion is reduced. Despite larger dislocation density, mostly contained by the LGLTBL, the FET yield on GaAs appears to be comparable to that on InP. Three-stage amplifiers have been demonstrated with low-frequency gain and bandwidth as high as 33 dB and 20 GHz, respectively.