5.59 W/mm Saturated Output Power Density at 30 GHz From E-Mode AlN/GaN HEMT Using Selective Etch of In Situ SiN Passivation Layer

This work reports on high-performance enhancement-mode (E-mode) AlN/GaN Schottky gate HEMT (AlN SGHEMT) for millimeter-wave applications. Utilizing an ultrathin 4-nm barrier of AlN tuned by the mechanical stress from in-situ SiN, and self-terminated etching technique, to form the E-mode AlN SGHEMT. As a result, the proposed device demonstrated positive threshold voltage ( ${V}_{\text {Th}}\text {)}$ of 0.53 V, high maximum drain current density ( ${I}_{\text {d- {max}}}\text {)}$ of 1.19 A/mm, and maximum transconductance ( ${G}_{\text {m- {max}}}\text {)}$ of $\sim ~0.61$ S/mm. Load-pull test was carried out at 30 GHz, which illustrated the ability of device to deliver a saturated output power density ( ${P}_{\text {sat}}\text {)}$ of 5.59 W/mm at a drain-source voltage ( ${V}_{\text {ds}}\text {)}$ of 25 V. The excellent results highlight a new approach to obtain mmW RF E-mode GaN HEMTs at Ka-band.