Symmetric metal nanogratings and horned shape extended pads to enhance light transmission of plasmonic metal-semiconductor-metal photodetector

In this work new plasmonic assisted metal-semiconductor-metal photodetectors are presented. The new devices incorporate symmetric triangular and elliptic gratings, subwavelength slit and metal pads that is extended into the active layer made up of GaAs. Simulations are carried out using the 2-D finite difference time domain method. It is shown that with elliptic nanogratings and optimized horned shape extended metal pads, light transmission through the subwavelength slit of the proposed structure is 17 times that of a plasmonic photodetector consisting of only a subwavelength slit at the middle of the metal contacts with no gratings. It is also demonstrated that the triangular shaped nanogratings fixes the peak transmission around the desired wavelength of 830 nm, while the rectangular and elliptic counterparts red shift the maximum transmission to about 900 nm.