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In recent years for the fabrication of millimetre wave circuits, the removal of the substrate has been proposed as a
solution for the reduction of losses, especially for silicon substrates. However, the micromachining of GaAs is an
exciting less explored alternative for manufacturing high performance communication systems. GaAs micromachining is
very interesting for the millimeter and submillimeter wave applications, due to the potential for easy monolithic
integration of passive circuit elements with active devices manufactured on the same chip.
This paper presents the monolithic integration of a two-director membrane supported Yagi-Uda antenna with a Schottky
diode, both having as support a 2 μm thick GaAs membrane. The design was based on the full-wave electromagnetic simulation software Zeland-IE3D. The following Molecular Beam Epitaxy (MBE) structure was grown on a
semiinsulating GaAs wafer: 0.2 μm thin AlxGa1-x As layer with x > 0.55 (the etch-stop layer) followed by a 2 μm Low
Temperature (LT) GaAs layer ("the membrane layer") and then by a 0.3 μm thin GaAs, (1x1018 cm-3-"ohmic layer").
Finally a 0.3 μm thin GaAs (1x1017 cm-3-"Schottky layer") was grown. An eight-mask process was developed for the
receiver manufacturing. The process includes some difficult steps regarding the integration of a very small Schottky
diode (with a diameter of about 3 μm) with the antenna with dimensions of a few millimeters, the polyimide-bridge
manufacturing, and the membrane formation using Reactive Ion Etching (RIE). The receiver characterization, including
the isotropic voltage sensitivity, was performed using "on wafer" measurements and has shown a good agreement with
the simulated results. High performance receiver circuits for operating frequency of 45 GHz have been demonstrated.
The technology developed can be used for applications up to THz.
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