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High Performance GaN High Electron Mobility Transistors on Low Resistivity Silicon for

This letter reports the RF performance of a 0.3-μm gate length AlGaN/AlN/GaN HEMT realized on a 150-mm diameter low-resistivity (LR) (σ <; 10 Ω · cm) silicon substrate. Short circuit current gain (f_T) and maximum frequency of oscillation (f_MAX) of 55 and 121 GHz, respectively, were obtained. To our knowledge, these are the highest f_T/f_MAX values reported to date for GaN HEMTs on LR silicon substrates.

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Shielded-Elevated Coplanar Waveguides (SE-CPWs) with low loss have been successfully developed for the first time for RF GaN on low-resistivity silicon (LR-Si) substrates (σ<;40 Ω·cm). Transmission losses (S21) of less than 0.4 dB/mm at X-band and better than 2 dB/mm at K-band with less than 20 dB return loss were exhibited by the developed SE-CPW, making them comparable in performance to those on traditional (semi-insulating) SI substrates. The developed waveguides use air-bridge technology to suspend CPW tracks above the HEMT GaN layer on LR-Si, directly above an additional thin layer of SiN and shielded ground planes. EM simulation was used to adjust structure parameters for performance optimization. In this work, we eliminated RF energy coupled into the substrate, paving the way for a cost-effective and higher integration GaN MMICs on LR-Si.

-Band Applications

In this paper, viable transmission media technology has been demonstrated for the first time on GaN on low-resistivity silicon) substrates (ρ <; 40 Ω·cm) at H-band frequencies (220-325 GHz). The shielded-elevated coplanar waveguide (CPW) lines employ a standard monolithic microwave integrated circuit compatible air bridge process to elevate the CPW traces above a 5-μm layer of benzocyclobutene on shielded metalized ground plates. An insertion loss of less than 2.3 dB/mm was achieved up to 325 GHz, compared with 27 dB/mm for CPW fabricated directly on the substrate. To prove the efficiency of the technology, a short-circuited stub filter with a resonant frequency of 244 GHz was used. The filter achieved an unloaded Q-factor of 28, along with an insertion loss of 0.35 dB and a return loss of - 34 dB. To our knowledge, these results are the best reported to date for GaN-based technology.

Novel Shielded Coplanar Waveguides on GaN-on-Low Resistivity Si Substrates for MMIC Applications

In this work a novel ultra-low loss transmission media for RF GaN-on-low-resistivity silicon (LR-Si) substrates (σ <; 40 Ω.cm) has been successfully demonstrated. The developed shielded-microstrip lines achieve comparable performance to those on semi-insulating (SI) GaAs substrates with transmission loss of 0.9 dB/mm for frequencies up to 67 GHz. Line performance was further enhanced by additional elevation of the shielded-microstrip lines using air-bridge technology above a 5 μm layer of benzocyclobutene (BCB) on shielded metalized ground planes. Transmission loss of 0.6 dB/mm for frequencies up to 67 GHz was obtained as a result of the extra elevation. Structure parameters were designed and optimized based on EM simulation for best performance. The work shows that the RF energy coupled into the substrate was eliminated, indicating the suitability of III-V-on-LR Si technology for millimeter-wave applications.

GaN on Low-Resistivity Silicon THz High-Q Passive Device Technology

In this work, a viable passive components and transmission media technology is presented for THz-Monolithic Integrated Circuits (THz-MIC). The developed technology is based on shielded microstrip (S-MS) employing a standard monolithic microwave integrated circuit compatible process. The S-MS transmission media uses a 5-µm layer of benzocyclobutene (BCB) on shielded metalized ground plates avoiding any substrate coupling effects. An insertion loss of less than 3 dB/mm was achieved for frequencies up to 750 GHz. To prove the effectiveness of the technology, a variety of test structures, passive components and antennas have been design, fabricated and characterized. High Q performance was demonstrated making such technology a strong candidate for future THz-MIC technology for many applications such as radar, communications, imaging and sensing.