A 2DEG-Based GaN-on-Si Terahertz Modulator with Multi-Mode Switchable Control

As terahertz (THz) technology has been widely considered as a key candidate for future sixth-generation wireless communication networks, THz modulators show profound significance in wireless communication, data storage, and imaging. In special, dynamic tuning of THz waves through 2D electron gas (2DEG) incorporated with a hybrid design of metasurface has attracted keen interest due to the combined merits of deliberate structural design, rapid switching speed and the process compatibility. Current meta-modulator enables very high modulation depth but encounter limited bandwidth. In this paper, by taking into account the co-functional effects of temperature and voltage-dependent dynamic control on transmission amplitude, a 2DEG-based GaN-on-Si modulator with two switchable operational states (or four modes) of active wave control is proposed. Under cryogenic temperature conditions, the proposed device exhibits prominent 2D plasmons characteristics with switchable transitions between the gated mode and ungated mode for active control. Under room temperature conditions, the proposed device exhibits non-resonance broadband spectra characteristics with tunable transitions between the linearity mode and depletion mode for transmission control. The scheme provides an option for the development of the actively tunable THz meta-modulator and paves a way for the robust multifunctionality of electrically controllable THz switching, and biosensors.