Investigation of the Effect of Different SiNx Thicknesses on the Characteristics of AlGaN/GaN High-Electron-Mobility Transistors in Ka-Band

The effect of different SiNx thicknesses on the performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) was investigated in this paper. The current, transconductance (G(m)), cut-off frequency (f(T)), maximum oscillation frequency (f(max)), power performance, and output third-order intercept point (OIP3) of devices with three different SiNx thicknesses (150 nm, 200 nm, and 250 nm) were measured and analyzed. The DC measurements revealed an increase in both the drain-source current (I-DS) and G(m) values of the device with increasing SiNx thickness. The S-parameter measurement results show that devices with a higher SiNx thickness exhibit improved f(T) and f(max). Regarding power performance, thicker SiNx devices also improve the output power density (P-out) and power-added efficiency (PAE) in the Ka-band. In addition, the two-tone measurement results at 28 GHz show that the OIP3 increased from 35.60 dBm to 40.87 dBm as the SiNx thickness increased from 150 nm to 250 nm. The device's characteristics improved by appropriately increasing the SiNx thickness.