Design and Fabrication of Implantable Neural Probes with Monolithically Integrated Light-Emitting Diodes for Optogenetic Applications

We report an implantable neural probe with monolithically integrated light-emitting diodes (LEDs) and recording site for optogenetic applications. The device were designed and fabricated with 2-inch gallium nitride on silicon epitaxial wafer. The neural probe consisted of three mu LEDs (a mesa size of 310 x 41 mm(2)) and four electrical recording sites, which had a total length of 6.72 mm (PCB bonding region + implanting region). The designed implantable neural probe was successfully processed by the conventional LED fabrication and Si microfabrcation. These methods can offer relatively rapid and easy fabrication. For fabricated mu LEDs, the optical and electrical properties were measured and characterized. At 1 mA, the emission wavelength was around 460 nm and it was slightly blue-shifted with the increase of injection current. Also, the optical power density was about 1 mW/mm(2) at an electrical input power of 3.5 mW, and it was increased to 6.3 mW/mm(2) at 24 mW.