Monolithic High Contrast Grating Integrated with Metal: Infrared Electrode with Exceptionally High Conductivity and Transmission

TL;DR

This paper introduces a monolithic GaAs high contrast grating integrated with metal (metalMHCG) that achieves high conductivity and transmittance for infrared transparent conductive electrodes, surpassing previous designs.

Contribution

The novel metalMHCG design effectively balances high electrical conductivity with high optical transmittance in infrared TCEs, addressing a key trade-off in the field.

Findings

Achieved 75% absolute transmittance of unpolarized light.

Sheet resistance ranged from 0.5 to 1 Ohm/Sq, lower than other TCEs.

Transmittance for polarized light reached 92% or 133% relative transmittance.

Abstract

The design of transparent conductive electrodes (TCEs) for optoelectronic devices requires a trade-off between high conductivity or transmittivity, limiting their efficiency. This paper demonstrates a novel approach to fabricating TCEs that effectively alleviates this trade-off: a monolithic GaAs high contrast grating integrated with metal (metalMHCG). The metalMHCG enables higher electrical conductivity than other TCEs, while providing transmissive and antireflective properties. We focus on infrared spectrum TCEs, which are essential for sensing, thermal imaging, and automotive applications. However, due to elevated free carrier absorption they are much more demanding than TCEs for the visible spectrum. We demonstrate 75% absolute transmittiance of unpolarized light, resulting in 108% transmittance relative to plain GaAs substrate. We achieved even larger absolute transmittance of polarized light, reaching 92% or 133% relative transmittance. Despite record high transmittance, the sheet resistance of the metalMHCG is several times lower than any other TCE, ranging from 0.5 to 1 Ohm/Sq.