Infrared SPR sensing with III-nitride dielectric layers

Abstract

In this work, Aluminum Indium Nitride (AlxIn1-xN) has been used as the dielectric overlay for a surface plasmon resonance sensor. The use of a ternary compound such as AlxIn1-xN for the dielectric allows a fine tuning of its refractive index by varying its composition, thus improving the sensor performance. Narrower transmittance resonances and higher sensitivities are obtained for transducers where the substrate rotates while depositing the ternary compound, which is attributed to the deposition of ternary layers with enhanced homogeneity. The calculated average sensitivity of the devices increases when rising the Al content of the dielectric layer, it being of 4360 nm/RIU, 5230 nm/RIU and 5730 nm/RIU for 0%, 36% and 100%, respectively. The device grown with 36% of Al shows the highest coupling strength. These results show the suitability of AlxIn1-xN compounds as dielectric layers in SPR sensors.