Terahertz Antenna Impedance Matched to a Graphene Photodetector

TL;DR

This paper presents a graphene-based terahertz photodetector with impedance matching techniques that achieve high sensitivity and room-temperature operation, advancing the development of efficient THz sensors.

Contribution

It introduces a novel impedance matching scheme for graphene THz detectors using a quasi-optical coupling and capacitor tuning, enhancing performance at room temperature.

Findings

Achieved NEP of less than 300 pW/√Hz at room temperature

Optimized antenna-graphene impedance matching for specific THz frequencies

Demonstrated scalable design suitable for far-infrared detection

Abstract

Developing low-power, high-sensitivity photodetectors for the terahertz (THz) band that operate at room temperature is an important challenge in optoelectronics. In this study, we introduce a photo-thermal-electric (PTE) effect detector based on quasi-free standing bilayer graphene (BLG) on a silicon carbide (SiC) substrate, designed for the THz frequency range. Our detector's performance hinges on a quasi-optical coupling scheme, which integrates an aspherical silicon lens, to optimize impedance matching between the THz antenna and the graphene p-n junction. At room temperature, we achieved a noise equivalent power (NEP) of less than 300 $pW/\sqrt{Hz}$. Through an impedance matching analysis, we coupled a planar antenna with a graphene p-n junction, inserted in parallel to the nano-gap of the antenna, via two coupling capacitors. By adjusting the capacitors and the antenna arm length, we tailored the antenna's maximum infrared power absorption to specific frequencies. The sensitivity, spectral properties, and scalability of our material make it an ideal candidate for future development of far-infrared detectors operating at room temperature.