Effect of Semiconductor on Sensitivity of a Graphene-Based Surface Plasmon Resonance Biosensor Goutam Mohanty 1 & Jamil Akhtar 2 & Bijay Kumar Sahoo 1 Received: 5 May 2015 /Accepted: 26 July 2015 # Springer Science+Business Media New York 2015 Abstract In this theoretical study, the effect of semiconductor on sensitivity of a graphene-based surface plasmon resonance (SPR) biosensor has been presented. Different semiconductors such as silicon (Si), germanium (Ge) and wurtzite III-V nitrides (AlN, GaN and InN) have been placed in between active silver (Ag) metal and graphene layer. Our simulation result shows that addition of semiconductor layer enhances the sensitivity by a factor of 3.76, 2.19, 3.82, 3.94 and 4.17 respectively for Si, Ge, InN, GaN and AlN. Also, we have examined the field enhancement factor due to above semiconductors and found maximum field intensity enhancement for the case of AlN. The analysis shows that best performance is achieved for red He-Ne laser light when optimized thicknesses of silver, AlN and graphene layer are 55, 14 and 0.34 nm (monolayer of graphene), respectively. More specifically, AlN would be a better choice for biosensing application in SPR biosensor. Keywords SPR biosensor . Semiconductor . Sensitivity . Field enhancement Introduction Surface plasmon resonance (SPR) is a simple and direct optical sensing technique that is used to investigate refractive index change that occurs in the vicinity of a thin noble metal film. The potential use of SPR for gas molecule detection and biosens- ing was first demonstrated by Nylander and co-workers [1, 2]. Later on, SPR biosensing has received a great attention from the scientific community. The advantage of employing SPR in bio- sensing lies in its capability of monitoring binding interactions without the need for labelling and fluorescence of the biomole- cules. In addition, this technique has shown great potential in the real-time determination of the concentration, kinetic constant and binding specificity of individual biomolecular interactions. Antibody–antigen interactions [3–5], peptide–protein interac- tions [6] and DNA hybridization [7] can all be analysed. In order to monitor surface interactions in a sensitive and stable manner with SPR biosensors, one should give attention in three vital areas. It is necessary that the SPR sensor is highly sensitive to binding interactions within the sensing region, the reflectivity dip has a narrow full-width-half-maximum (FWHM) and the metal film is highly stable even under ex- treme environmental conditions [8]. Due to different optical and chemical properties of individual metal films, the realization of all three conditions is not possible simultaneously with a con- ventional SPR sensor. The choice of metal used is critical since the metal must exhibit free electron behaviour as described by the free electron model. To be useful for SPR, a metal must have conduction band electrons capable of resonating with light at a suitable wavelength. Silver [9] and gold [10] are two such metallic elements that satisfy this condition, and they are more popularly used in research and commercial applications be- cause of their sensitivity and stability, respectively. Instead of the above-mentioned metals, other metals like copper, alumin- ium and palladium may be used over the prism surface. The drawback with gold is that it is a poor adsorbent of biomolecules, thereby limiting the sensitivity of the biosensor. Generally, a silver film with a sharp SPR curve may yield a higher imaging sensitivity than a gold film. However, the sen- sitivity of the silver-based SPR biosensor has a potential * Goutam Mohanty gmohanty.phd2012.phy@nitrr.ac.in 1 Department of Physics, N.I.T Raipur, G. E. Road, Raipur, CG 492010, India 2 Sensor and Nanotechnology Group, CSIR-CEERI, Pilani, Raj 333031, India Plasmonics DOI 10.1007/s11468-015-0033-0