4.2 W/mm at 10 GHz in silicon delta-doped AlN/GaN/AlN pseudomorphic HEMTs with PECVD SiN passivation

We demonstrate AlN/GaN/AlN pseudomorphic high electron mobility transistors (pHEMTs) on bulk AlN substrates with silicon δ-doping near the bottom of the 20-nm GaN channel. Our recent studies on epitaxy and low-field transport show that δ-doping in pseudomorphic AlN/GaN/AlN heterostructures increases electron mobility and two-dimensional electron gas density while preserving the advantages of the thin GaN channel, compared to undoped counterparts. In this work, we present DC and RF characteristics of these pHEMTs with PECVD SiN passivation, exhibiting an average f_T·L_G product of 12.5 GHz·μm, a representative output power density of 4.2 W/mm with an associated power-added efficiency of 41.5% at 10 GHz.