A 4W Heterogeneous Power Amplifier with GaN-on-Si Dielets in Single-Crystal Diamond Interposer for 6G FR3 Applications

This paper presents the design and fabrication of a heterogeneous power amplifier (PA) incorporating gallium nitride (GaN) high electron mobility transistor (HEMT) dielets into a single-crystal diamond interposer platform. 12×100 µm GlobalFoundries 130RF GaN high electron mobility transistors (HEMT) are singulated using femtosecond laser to a size of 274 µm × 400 µm for the fabrication of single transistor dielets. The diamond interposer is able to provide heat spreading, packaging and circuit build up for the dielet. The interposer features 2 redistribution layers (RDL) for metallization fabrication. The effects of the interposer on dielet load pull performance are analyzed. At 10 GHz, a 1.8 dB increase in output power (Pout), 1.5% increase in maximum power added efficiency (PAE), and a 0.3 dB increase in gain is observed. These insights guide the design of a power amplifier (PA) for 6G FR3 applications with a 3 dB bandwidth (BW) of 6.8–10.3 GHz that is able to provide up to 4 W of output power. From 8–10 GHz, the PA has a PAE ranging from 39.2–49.1% with respectable performance at 6 dB back off.