Electro-optic metal–insulator–semiconductor–insulator–metal Mach-Zehnder plasmonic modulator

Abstract

The performance of a CMOS-compatible electro-optic Mach-Zehnder plasmonic modulator is investigated using electromagnetic and carrier transport simulations. Each arm of the Mach-Zehnder device comprises a metal–insulator–semiconductor–insulator–metal (MISIM) structure on a buried oxide substrate. Quantum mechanical effects at the oxide/semiconductor interfaces were considered in the calculation of electron density profiles across the structure, in order to determine the refractive index distribution and its dependence on applied bias. This information was used in finite element simulations of the electromagnetic modes within the MISIM structure in order to determine the Mach-Zehnder arm lengths required to achieve destructive interference and the corresponding propagation loss incurred by the device. Both inversion and accumulation mode devices were investigated, and the layer thicknesses and height were adjusted to optimise the device performance. A device loss of <8dB is predicted for a MISIM structure with a 25nm thick silicon layer, for which the device length is <3μm, and <5dB loss is predicted for the limiting case of a 5nm thick silicon layer in a 1.2μm long device: in both cases, the maximum operating voltage is 7.5V.