Electro-optical effect in hydrogenated amorphous silicon-based waveguide-integrated p-i-p and p-i-n configurations

A p-i-p configuration of an electro-optical modulator based on hydrogenated amorphous silicon (a-Si:H) is characterized and compared with an a-Si:H based p-i-n modulator. In particular, we estimate the performances in terms of optical losses, voltage-length product, and bandwidth at γ = 1550 nm for waveguide-integrated p-i-p versus p-i-n configurations. Both devices are fabricated on a silicon substrate by plasma enhanced chemical vapor deposition at low temperature ensuring the back-end integration with a CMOS microchip. We demonstrate a factor of merit for the p-i-p waveguide integrated Fabry-Perot resonator of Vp × Lp = 19 V × cm allowing the design of shorter devices with respect to p-i-n structure.