Large-Area Metal-Integrated Grating Electrode Achieving Near 100% Infrared Transmission

TL;DR

This paper introduces a large-area, metal-integrated high-contrast grating electrode on GaAs that achieves near 100% infrared transmission with high electrical conductivity, advancing infrared optoelectronic device performance.

Contribution

The study presents a novel metal-integrated high-contrast grating electrode that significantly improves infrared transparency and conductivity, setting a new benchmark for TCEs in the mid- to far-infrared range.

Findings

94% transmission at 7 micrometers wavelength

Sheet resistance of 2.8 ohms per square

135% transmission relative to flat GaAs-air interface

Abstract

Highly transparent and conductive electrodes operating in the infrared (IR) are critically needed for a broad range of technologies, including light-emitting diodes, lasers and photodetectors, which are key building blocks of infrared cameras, LiDARs, and thermal systems such as IR heaters. While transparent conductive electrodes (TCEs) have seen substantial progress in the visible spectrum, their performance in the IR remains limited due to increased absorption and reflection caused by the plasma resonance of free carriers in conductive materials. Here, we demonstrate a large-area TCE based on a metal-integrated monolithic high-contrast grating (metalMHCG) fabricated on a GaAs substrate. This structure acts as an effective antireflection coating, achieving near-unity transmission of unpolarized mid- to far-infrared (M-FIR) light. The metalMHCG exhibits 94% transmission at a wavelength of 7 micrometers, corresponding to 135% relative to transmission through a flat GaAs-air interface, while maintaining an exceptionally low sheet resistance of 2.8 ohms per square. By simultaneously delivering excellent optical transparency and electrical conductivity, the metalMHCG establishes a new performance benchmark among M-FIR TCEs and provides a versatile platform for next-generation high-power optoelectronic devices.