High-fMAX High Johnson's Figure-of-Merit 0.2-μm Gate AlGaN/GaN HEMTs on Silicon Substrate With AlN/SiNx Passivation

This letter reports a 0.2-mu m gate AlGaN/GaN high-electron-mobility transistors (HEMTs) on an Si substrate passivated with an AlN/SiNx (4/20 nm) stack layer. The 4-nm-thick AlN was grown by plasma-enhanced atomic-layer-deposition. The AlN/SiNx-passivated HEMTs exhibit a high maximum drain current of 930 mA/mm, an three-terminal OFF-state breakdown voltage (BVDS) of 119 V, and a small threshold voltage shift of 130 mV in a wide drain bias range (V-DS = 3 - 24 V). Owing to the additional positive polarization charge in the AlN passivation layer, the access resistance R-s in the GaN-on-Si HEMTs is significantly reduced while maintaining small parasitic gate-drain capacitance C-gd, contributing to a high power-gain cutoff frequency f(MAX) of 182 GHz and a high Johnson's figure of merit of BVDS x f(T) of 6.43 x 10(12) V/s simultaneously. The accuracy of the RF performance is verified by a small signal modeling based on measured S-parameters.