Active terahertz metamaterials electrically modulated by InGaZnO Schottky diodes

Active metamaterials (MTMs) are artificially engineered structures with tunable and exceptional properties that are absent in natural materials. Recently, InGaZnO (IGZO), a widely used semiconductor for large-area and flexible display backplane drivers, has gained interest for active control of MTMs due to its large-area uniformity, ease of thin film deposition, and low cost. In this paper, IGZO Schottky barrier diodes (SBDs) are proposed to reconfigure electric-field-coupled inductor-capacitor (ELC) MTMs and actively control terahertz (THz) waves for the first time. The SBDs are designed to bridge the capacitors of the ELC resonators so that the average conductivity within the capacitor gap can be modulated by bias voltage while keeping the capacitance value almost unchanged. To precisely simulate this mechanism, two U-shaped resistive sheet models beside the gap are built for IGZO SBD in 3-D simulation for maintaining the same capacitance and resonant frequency. Furthermore, a device with 14400 MTM cells is fabricated and characterized using frequency-domain spectroscopy. The measured transmission shows a continuous modulation from -14.2 to -9.4 dB at 0.39 THz, which corresponds to a modulation depth of 14.3%. This work paves a new way for active THz MTMs using industrial compatible thin-film technology.