GaN biosensor design with localized surface plasmon resonance

The need for rapid, compact, and accurate biosensing capability has increased dramatically in recent times in biomedical and environmental applications. Optical biosensing is one of the most promising methods for virus and chemical substance detection. With analytes or substance binding to the ligands that are attached to the surface or nanoparticles, the optical spectra shift accordingly resulting in detection of a specific substance. Localized surface plasmon resonance (LSPR) technique can be applied to enhance the detection sensitivity, providing an improvement on optical biosensor devices. However, the literature on wide bandgap GaN-based optical biosensor utilizing LSPR is limited, even though GaN-based visible optoelectronic devices have been widely implemented in various applications. Thus, it is important to design and optimize the GaN-based biosensors for their use in optical biosensing applications. In this work, optical properties of GaN-based structure with LSPR effect are investigated using the Finite-Difference-Time-Domain (FDTD) simulation method. GaN-based structures are constructed with nanoparticles coated on GaN surface. The nanoparticles are designed taking into consideration the size and metal elements such as gold, silver, and titanium. A modified refractive index-varying layer is incorporated to mimic the substance attachment on the structure surface. Electric field spectra show that optimizing the GaN-based structures will lead to the LSPR effect, confirming its potential for biosensing applications In addition, the optical spectra of the GaN-based sensor structures show sharp shifts (~ 4 nanometers per .01 refractive index change) when the refractive index of the substance layer is tuned.