High-Performance MMIC Inductors for GaN-on-Low-Resistivity Silicon for Microwave Applications

Novel MMIC spiral inductors on GaN-on-low-resistivity silicon (LR-Si) substrates (σ <; 40 Ω · cm) are demonstrated with enhanced self-resonance frequency ( fSRF) and Q-factor. The developed technology improves inductor performance by suppressing substrate coupling effects using air-bridge technology above benzocyclobutene dielectric as an interface layer on the lossy substrate. A 0.83-nH spiral inductor with peak Q-factor enhancement of 57% (Q = 22 at 24 GHz) and maximum fSRF of 59 GHz was achieved because of the extra 5-μm elevation in air. An accurate broad-band model for the fabricated inductors has been developed and verified for further performance analysis up to 40 GHz. The proposed inductors utilize cost-effective, reliable, and MMIC-compatible technology for the realization of high-performance RF GaN-on-LR Si MMIC circuits for millimeter-wave applications.