Polarization Properties in AlGaN/GaN HEMT-Array with a Shifted Gate

We describe the plasmon resonances of AlGaN/GaN HEMT-array with a shifted gate at THz frequencies. By altering gate voltage and gate length, we obtained absorption spectra at different gate positions using the Drude dispersion to model the conductive channel layer. We observed that the asymmetry of the device's gate position has no effect on the first-order mode of absorption but significantly impacts the second-order or higher-order modes. Through the electric field distribution, it can be found that in the first-order mode, different gate positions do not affect the electric field distribution. But in higher-order modes, when the gate is close to the source or drain, the 2D plasmons in the gated region will couple with the ungated 2D plasmons in the source and drain regions. In our simulation, the asymmetric gate position will have a higher absorption peak in the high-order mode. At the same time, the asymmetric gate structure under high-order mode can also reach higher modulation depth. The studies of these characteristics may have promising applications including high-responsivity quantum-dot THz detection, THz modulator, and other electrically tunable THz devices.