6C-5 Planar Integration of SAW Filter with HEMT on AlGaN/GaN Heterostructure Using Fluoride-based Plasma Treatment

We demonstrate a new planar fabrication technology for integrating surface acoustic wave (SAW) filters with high-electron mobility transistors (HEMTs) on AlGaN/GaN heterostructures using fluoride-based (CF₄) plasma treatment techniques. The CF₄ plasma treatment has been shown capable of effectively depleting the two-dimensional electron gas (2DEG) without removing the top AlGaN layer. It is not only able to achieve the same level of active device isolation, but also able to permit the acousto-electric transductions in the interdigital transducers (IDTs) of the SAW filters. The RF characteristics of the planar SAW filter was similar to those of SAW filters directly fabricated on GaN layer exposed by using the mesa etching. Compared to the SAW device without HEMT, the integrated SAW/HEMT exhibited an insertion loss that was 5.129 dB lower because of the amplification by the output HEMT