Design of ungrounded CPW GaN-on-Si MMICs

This work presents a study of circuit component design in a new GaN-on-Si process being developed by the MIT Lincoln Laboratory. The process uses a thick silicon substrate with no through-vias with a multi-layer stack-up. Examples of components required for MMIC design include lines of various impedances, shorted and open stubs, tees, meander lines, and capacitors. Because the fabrication process requires the use of ungrounded CPW lines, underpasses are necessary to connect ground planes and a study of 50-Ohm lines with several underpass spacings is performed. The large range of dimensions and dielectric constants presents a challenge for full-wave simulations, and a comparison between Ansys HFSS and Sonnet Software is presented for a variety of passive circuit components implemented in the GaN-on-Si MMIC stack-up.