Enhancement in Analog/RF and Power Performance of Underlapped Dual-Gate GaN-Based MOSHEMTs with Quaternary InAlGaN Barrier of Varying Widths

An underlapped dual-gate (U-DG) quaternary In_0.05Al_0.75Ga_0.2N/GaN metal–oxide–semiconductor high-electron-mobility transistor (MOS-HEMT) and a conventional ternary Al_0.3Ga_0.7N/GaN MOS-HEMT device with the same structure are analyzed and compared by investigating their analog/radiofrequency (RF) and power performance. Quaternary InAlGaN heterostructures, having higher polarization charge density, exhibit almost three times higher two-dimensional electron gas (2DEG) concentration, thus showing 171.8% higher saturation drain current density (I_d) compared with ternary AlGaN having an equal barrier width of 18 nm, at the same working voltage of 1 V, thus validating the improved analog performance. The influence of the InAlGaN barrier layer on all the performance parameters is studied by varying its thickness for three different widths (18 nm, 13 nm, and 7 nm). The 10.8% higher f_T and 9.1% higher f_MAX values of the InAlGaN MOS-HEMT with respect to the AlGaN counterpart prove the former’s superiority for use in high-frequency amplifiers. These percentage improvements increase to 18.3% and 54.6%, respectively, for the smaller quaternary barrier width of 7 nm. Large-signal analysis for the 7-nm InAlGaN/GaN MOS-HEMT at 100 GHz indicates a higher gain with 87.5% output power efficiency compared with 42.5% for the 18-nm AlGaN/GaN MOS-HEMT at the same input of 45 dBm, demonstrating that the thinner-barrier quaternary MOS-HEMTs is a better candidate for use in sophisticated high-power devices.