Characterization of Coplanar Waveguides
on AlGaN/GaN HEMT on Silicon Buffer Layers up to 110 GHz

Diego Marti, Mathias Vetter, Liang Liu, Andreas R. Alt, Hansruedi Benedickter, E. Piner,1) and C. R. Bolognesi*
Millimeter-Wave Electronics Group, ETH-Zürich, Gloriastrasse 35, Zürich 8092, Switzerland
1) Nitronex Corporation, Durham NC 27703, USA, (Now at Texas State University)
*Corresponding author email:


In the present work we report the characterization of coplanar waveguides (CPWs) implemented on AlGaN/GaN HEMT layers deposited on high-resistivity silicon (HR-Si) substrates, up to frequencies as high as 110 GHz. The topic is of interest because it is fairly widely held in the community that substrate losses could hinder the application of GaN HEMTs on silicon at millimeter-wave frequencies. We demonstrate that conventional CPWs on AlGaN/GaN on HR-Si HEMT layers show a loss of 0.8 dB/mm at 110 GHz. Furthermore, etching trenches between the CPW conductors is an effective and manufacturable method to further reduce losses, and enables attenuation levels as low as ~0.6 dB/mm at 110 GHz. This work shows that CPWs on GaN-on-Si exhibit performances that are comparable to those built on S.I. InP, clearly demonstrating the applicability of GaN-on-Si technology in mm-wave applications.

Paper 7b.2.pdf