Wavelength-selective enhancement of terahertz absorption of metallic grating/GaAs-based hybrid photoconductive detector

Abstract

Terahertz (THz) technology has attracted significant research attention because it can be used for a host of applications, such as astronomical observations, security checks, material optimization, and biomedical treatment. In this work, we fabricate an extrinsic n-type GaAs photoconductive detector whose peak photoelectric response is demonstrated to be at about 255 μm. To improve device performance in a long-wave (>350 μm) domain and overcome the epitaxial-growth bottleneck, we designed hybrid structural GaAs-based photoconductive detectors on the surface of which we add subwavelength one-dimensional metallic gratings (i.e., with grating periods that range from 100 to 125 μm) and investigated the wavelength-selective enhancement of their absorption in the THz regime by using a finite-different time-domain simulation. The simulation results indicate that selective enhancement of antireflection and absorption occurs in the reflection and absorption spectra so that the peak wavelength of photoelectric response can be extended to over 400 μm and the thickness of absorption layer can be reduced to 50 μm. The electric-field intensity of the incident THz wave can be significantly enhanced near the interface between the metal gates and the absorption layer. This work can thus provide a potential scheme to fabricate high-performance THz detectors for numerous applications.