High-Efficiency InGaAs/InP Photodetector Incorporating SOI-Based Concentric Circular Subwavelength Gratings

A grating-integrated silicon-on-insulator (SOI)-based photodetector for use in the long wavelength was fabricated and characterized. An InGaAs/InP p-i-n structure was heterogeneously integrated on an SOI-based concentric circular subwavelength grating (CC-SWG) by means of a low-temperature bonding process with benzocyclobutene as the bonding agent. The light absorption of the device is enhanced due to high-index-contrast CC-SWGs as a broadband reflector. These features lead to an increase in quantum efficiency, for the whole S, C, and L communication bands, while maintaining a high speed. The measured quantum efficiency was increased by 39.5% with CC-SWGs in comparison with the device without gratings. A quantum efficiency of 53% at a wavelength of 1.55 and a 3-dB bandwidth of 25 GHz at a reverse bias of 3 V were simultaneously obtained in the device.