Analysis of Fringing Effect on Resonant Plasma Frequency in Plasma Wave Devices

The effect of fringing electric field due to the nonideality of the gate two-dimensional electron gas (2DEG) channel capacitance on the fundamental resonant frequency of plasma waves in a high-electron-mobility transistor (HEMT) channel was investigated. The spatial distribution of sheet electron density in the fringed region of the 2DEG channel and the expression for the fundamental resonant frequency of plasma oscillation were obtained. A cascaded transmission line (TL) equivalent circuit model was developed to represent the gated and ungated fringed regions of the HEMT 2DEG channel. Results of calculation and IsSpice simulation show that fringing effects can be the cause of the fundamental plasma frequency reduction. Thus, the developed fringing effect model improves the deviation between theoretical and experimental data.