High-speed short wavelength silicon photodetectors fabricated in 130nm CMOS process

Abstract

We have integrated several optoelectronic devices into deep-submicron silicon fabrication process. The results for integration of silicon planar interdigitated P-I-N photodiodes with transimpedance amplifiers and waveguide grating couplers will be presented. The integration process was carried out in an unmodified 130nm CMOS integration process, on silicon-on-insulator (SOI) substrates. Photodetectors that were fabricated on 200nm-thick SOI exhibited a 3dB electrical bandwidth of l0GHz for -5V, bias while the photodetectors fabricated on 2μm-thick SOI had 8GHz 3dB electrical bandwidth for -28V bias. The external quantum efficiency of the 2μm-thick photodetectors at 835nm was 14%. The 200nm-thick photodetectors were integrated with waveguide grating couplers. The external quantum efficiency of the photodetector at 830nm improved from 3% to 12% when a diffraction grating with 265nm period was integrated on top of the photodiode. Monolithically integrated optical receivers were fabricated on 2μm-thick SOI substrates. Sensitivities for BER of 10-9 of -15.4dBm and -10.9dBm were measured for 3.125Gb/s and 5Gb/s, respectively. The dynamic range was 17.5dB and 13dB, at 3.125Gb/s and 5Gb/s. Error free operation was possible up to 8Gb/s. The 2μm- thick SOI photodetectors were wire-bonded to SiGe transimpedance amplifiers with 184Ω transimpedance gain. When the photodiode was used in avalanche operation mode the sensitivity of -7dBm (BER<10-9) was achieved at 10Gb/s. This is the highest speed reported for an all-silicon optical receiver.