Optoelectronic detectors and receivers: speed and sensitivity limits

This invited paper first reviews the recent advances in the area of photodetectors and optoelectronic integrated circuit (OEIC) receivers for the preferred 1.55 /spl mu/m light-wave fiber-optic communication links. The m-s-m (metal-semiconductor-metal) and the p-i-n photodetectors are based on lattice-matched InGaAs photoabsorption layers on semi-insulating InP substrates, and the receiver integrates one of these photodetectors with a low-pass high bandwidth amplifier based on either compatible heterostructure bipolar or field-effect transistors (HBTs or HFETs) and passive resistors. The primary focus of this paper is on: (a) the theoretical and experimental results identifying the high-frequency limits of different types of photodetectors, (b) an optimized design approach to p/sup +/(n/sup -/)p/sup +//HBT and n/sup +/(p/sup -/)n/sup +//HFET OEIC transimpedance receivers with flat frequency response, and (c) their speed and sensitivity limits in the presence of the background device and circuit noise, and the inter-symbol interference (ISI). The transit-time limited frequency response of the photodetectors is found to be directly proportional to the slower hole carrier effective velocity, and inversely proportional to the effective separation of the detector's electrodes. For m-s-m photodetectors with metallization width and separation of 0.25 /spl mu/m, and for vertical p-i-n photodiodes with 0.2 /spl mu/m electrode separation the 3-dB bandwidth limits of both devices are found to be approximately 80 GHz. Similar frequency limits can be obtained from IC compatible p/sup +/(n/sup -/)p/sup +/ or n/sup +/(p/sup -/)n/sup +/ surface-oriented lateral photodetectors. When these detectors are integrated together with compatible transistors having comparable current gain cut-off frequency (f/sub c/), either in p/sup +/(n/sup -/)p/sup +//HBT or n/sup +/(p/sup -/)n/sup +//HFET OEIC receivers with optimized transimpedance (/spl cong/1.5 k/spl Omega/), the expected bit-rate and sensitivity limits are shown to exceed 31 Gb/s and -22 dBm, respectively.