Michael Schlechtweg

In this letter, the realization of planar zero bias Schottky diodes on an InGaAs metamorphic high-electron-mobility transistor (mHEMT) MMIC technology is presented. The aim is to investigate the optimum performance for detector applications in an integrated MMIC solution. Device optimization was performed, by analyzing the voltage responsivity of each single diode variation. Voltage responsivities of up to 18000 V/W at W-band frequencies on an intrinsic diode level were achieved. Furthermore, a detector MMIC centered around 105 GHz was realized with a maximum voltage responsivity of 7700 V/W.

In this paper, we present the development of submillimeter-wave monolithic integrated circuits (S-MMICs) and modules for use in next-generation sensors and high-data-rate wireless communication systems, operating in the 300-500-GHz frequency regime. A four-stage 460-GHz amplifier MMIC and a 440-GHz class-B frequency doubler circuit have been successfully realized using our 35-nm InAlAs/InGaAs-based metamorphic high-electron mobility transistor (mHEMT) technology in combination with grounded coplanar circuit topology (GCPW). Additionally, a 500-GHz amplifier MMIC was fabricated using a more advanced 20-nm mHEMT technology. To package the submillimeter-wave circuits, a set of waveguide-to-microstrip transitions has been fabricated on both 50-μm-thick quartz and GaAs substrates, covering the frequency range between 220 and 500 GHz. The E-plane probes were integrated in a four-stage 20-nm cascode amplifier circuit to realize a full H -band (220 to 325 GHz) S-MMIC amplifier module with monolithically integrated waveguide transitions.

While for decades radars in the 94-GHz region of the electromagnetic spectrum were mainly developed for military applications, nowadays a range of other applications mainly concerning security and safety can be served by miniaturizes millimeterwave radars. The technology is considerably different from that used in the past. One terminal devices like Gunn- and IMPATT oscillators with limited bandwidth and Schottky barrier mixers with also limited noise performance were the key components in the past, while today LNAs and MPAs / HPAs exhibiting nearly full waveband performance and low noise figures are in common use. The paper describes the effort to develop an experimental, miniaturized 94-GHz radar for different applications. Specific applications mainly require a specially designed antenna, but can rely on the same radar frontend.

This paper presents an overview on selected results in the area of millimeter-wave and sub-millimeter-wave integrated circuits and devices in Europe for application in the frequency range between 100 GHz and 2THz. Advanced integrated circuits for millimeter-wave applications based on metamorphic InAlAs/InGaAs HEMTs on 4" GaAs substrates were developed and manufactured at the Fraunhofer Institute IAF. An extrinsic transit frequency of 410 GHz for 50 nm gate length devices is achieved. Two-stage low-noise amplifiers demonstrate a small signal gain of 20 dB and a noise figure of 2.4 dB at 94 GHz. An amplifier MMIC developed for G-band operation exhibits a gain of 21 dB at 220 GHz. These results are compatible with those achieved using state-of-the-art InP-based HEMT technologies. Recent results of HBVs (heterojunction barrier varactors), Schottky diodes and HEBs (hot-electron bolometers) for signal generation and detection up to terahertz frequencies obtained by various research groups in Europe are presented

A dry etch process based on Cl₂/SF₆ has been developed to selectively remove GaN over AlGaN for the fabrication of recessed gate GaN/AlGaN HEMTs. Using this etching process recessed and non-recessed FETs were fabricated side by side on the same wafer to provide a fair comparision of data. Recessed gate FETs with a gatelength of 0.15μm show cutoff frequencies of 83 and more than 200 GHz for fT and fmax, respectively. Furthermore, gate-drain breakdown as high as 84V has been obtained which is more than twice as much compared to their non-recessed counterparts.