CMOS-compatible all-Si high-speed waveguide photodiodes with high responsivity in near-infrared communication band

Abstract

Submicrometer silicon photodiode waveguides, fabricated on silicon-on-insulator substrates, have photoresponse from <1270 to 1740 nm (0.8 AW-1 at 1550 nm) and a 3-dB bandwidth of 10 to 20 GHz. The p-i-n photodiode waveguide consists of an intrinsic waveguide 500 × 250 nm where the optical mode is confined and two thin, 50-nm-thick, doped Si wings that extend 5 μm out from either side of the waveguide. The Si wings, which are doped one p-type and the other n-type, make electric contact to the waveguide with minimal effect on the optical mode. The edges of the wings are metalized to increase electrical conductivity. Ion implantation of Si+ × 1013 cm-2 at 190 keV into the waveguide increases the optical absorption from 2-3 dB · cm-1 to 200-100 dB cm-1 and causes the generation of a photocurrent when the waveguide is illuminated with subbandgap radiation. The diodes are not damaged by annealing to 450 ° C for 15 s or 300 °C for 15 min. The photoresponse and thermal stability is believed due to an oxygen stabilized divacancy complex formed during ion implantation. © 2007 IEEE.