E-Beam Fabricated Metal-Semiconductor-Metal (Msm) Varactor Based On Algan/Gan Hemt With Rectangular Gate Of 450nm

The fabrication and characteristics of balanced metal-semiconductor-metal (MSM) two-dimensional electron gas (2DEG) varactors based on AlGaN/GaN high electron mobility transistor (HEMT) for terahertz circuits were presented. The cathodes were designed to he strip-gates with submicron length of similar to 450nm and manufactured by using electron beam lithography (EBL). The anodes lengths are ranging from similar to 450nm to similar to 2 mu m to study the influence of anode size on DC and high frequency characteristics. The DC and high frequency measurements were carried out, current-voltage and capacitance-voltage characteristics were investigated. As increasing the size of anode size to 2 mu m, the cutoff frequency of the MSM varactors was increasing as well. By matching the equivalent circuit at zero bias voltage with anode size of 2 mu m, the series resistance (R-0) of similar to 32.43 Omega, and the capacitance (C-0) of similar to 5.09 fF were abstracted respectively, and the cutoff frequency of similar to 964.6 GHz and the figure of merit (FOM) of 4.07 THz were obtained.