Dual-band electrically reconfigurable terahertz metasurface enabled by AlGaN/GaN HEMTs.

Terahertz (THz) metasurfaces with efficient and electrically reconfigurable electromagnetic responses are highly desired for emerging wireless communication systems. However, realizing compact solid-state active THz devices with multiband modulation capability remains challenging. Here, we demonstrate a dual-band electrically reconfigurable THz metasurface enabled by AlGaN/GaN high-electron-mobility transistors (HEMTs). The dual-band response originates from two cavity modes supported by the reflective metal-insulator-metal (MIM) structure, while the gate-controlled two-dimensional electron gas (2DEG) channel tunes the effective surface admittance of the HEMT-integrated metasurface. The fabricated device achieves reflection amplitude modulation depths of 59% and 94% at 0.245 and 0.429 THz, respectively, together with maximum phase shifts of 35∘ and 180∘ at 0.238 and 0.425 THz. This work extends AlGaN/GaN HEMT-based THz modulation toward dual-band operation, offering enhanced frequency-domain flexibility for wireless communications and spectroscopic sensing.