Transparent conductive electrodes based on GaAs-metal deep sub-wavelength high contrast grating
Résumé
A highly transparent and conductive electrode formed of a GaAs-based monolithic high-contrastgrating combined with an array of metal nanowires (mMHCG) operating in the near-infrared rangeis presented. Designed for the transmission of selected TE or TM polarized light around the 940 nmwavelength, the fabricated mMHCG demonstrates a remarkable light transmittance level of 85%,surpassing the Fresnel threshold by 16%, which corresponds to a relative transmittance of 122%with respect to the transmission through plain GaAs-air interface. Additionally, these structuresexhibit low sheet resistance of 1.4 Ω/sq. We achieve this performanceby fabricating semiconductordeep subwavelength monolithic high-contrast gratings integrating metal stripes placed either in therecesses or on top of the etched semiconductor gratings. The high transmittance of polarised lightthrough the mMHCG is demonstrated for the first time in the near-infrared range thanks to lowquality factor resonance tunnelling the light through semiconductor stripes in the TE configurationand through the air slots between semiconductor stripes in the TM configuration. This work servesas conclusive evidence of mMHCG's extraordinary transparency and low sheet resistance, despitethe significant challenges in the near-infrared spectral range posed by high free carrier absorptionand the nanoscale precision required for mMHCG fabrication. This work demonstrates theextension of the mMHCG approach as an efficient transparent conductive electrode intooptoelectronic devices such as LEDs, vertical-cavity surface-emitting lasers (VCSELs), andphotodetectors