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

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.