Simulation on absorption properties of Terahertz metamaterial/GaAs based photoconductive detector

Terahertz (THz) technology, used for astronomical observation, security check, material optimization and biomedical treatment, has attracted various attentions all over the world. Extrinsic GaAs photoconductive detector, as a typical THz detector, requires an enough thick high-purity GaAs epitaxial absorption-layer to get a good performance. However, such thick GaAs epitaxial layers are difficult to grow and would induce large dark current. A new structure designed by adding split ring resonator as Terahertz metamaterial on traditional GaAs based photoconductive device was proposed in this work, and its absorption spectrum was investigated by FDTD simulation. The simulation results indicated that by inducing metamaterial to GaAs photoconductive detector, obvious absorption enhancement effect occurs at the resonance frequency (0.75THz). This novel structure largely reduced the thickness of absorption-layer to 15μm, and enhanced the absorption of incident THz wave at about 400μm. Our design provides a novel device to solve the epitaxial growth bottleneck of GaAs epitaxial photoconductive detector.