Abstract
High performance coplanar waveguides (CPWs) on GaN membrane technology for AlGaN/GaN high electron mobility transistors (HEMTs) grown on low-resistivity (LR) Si substrates have been demonstrated in this work. The developed CPW technology shows a remarkable improvement in RF losses when the lossy Si beneath CPW structures is removed, resulting in comparable RF performance to that of CPW realized on high-resistivity (HR) Si and semi-insulating (SI) SiC substrates, with similar AlGaN/GaN top epitaxial layers. Experimental results, first to be reported, demonstrate transmission losses ( $S_{21}$ ) of 0.47 dB and $Q$ -factor of 20.77 for the CPW on GaN membrane technology, compared to $S_{21}$ of 2.95 dB and $Q$ -factor of 4.51 for the CPW on GaN-on-LR Si, at 40 GHz. Furthermore, the influence of substrate parasitics on RF performance of CPW on GaN-based HEMTs grown on various substrates was studied and analyzed by the extraction of transmission line parameters for frequencies up to 40 GHz. These findings offer viable integrated GaN-based HEMTs on LR Si technology suitable for high-power and high-temperature system applications at RF and millimeter-wave frequencies, when used in conjunction with high thermal coefficient materials such as diamond and AIN.
Published Version
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