High-efficiency and high-speed metal-semiconductor-metal photodetectors on Si-on-insulator substrates with buried backside reflectors

We report Si metal-semiconductor-metal photodetectors with high-efficiency and high-speed in the infrared using Si-on- insulator substrates with backside reflectors buried underneath a deep-submicron-thick active layer. The reflectors cause the trapping of the light inside the thin Si active layer, resulting in a fast and efficient carrier- collection by the electrodes. The impulse response of the photodetector, measured by electro-optic sampling at 780 nm wavelength, has a full width at half-maximum of 5.4 ps, corresponding to a 3-dB bandwidth of 82 GHz. At both 633 and 850 nm wavelengths, the responsivities of the photodetectors with the buried backside reflectors are at least an order of magnitude larger than that of those without the reflectors.