<title>Monolithically integrated silicon NMOS-PIN photoreceiver</title>

Abstract

For large-volume optoelectronics applications, the low cost, manufacturability and reliability of silicon MOSFET technology are advantageous. In addition, silicon photodetectors operate quite efficiently at the 0.8 micrometers wavelength of economical AlGaAs light sources. In this letter, we report on a silicon-based monolithic optical receiver. A symmetric transimpedance preamplifier was designed and simulated for depletion-mode NMOS with L_gate equals 1 micrometers and V_T equals -0.1 V. The symmetric circuit provides insensitivity of dc bias point to FET threshold voltage deviation. The silicon photodiode is a planar p-i-n structure with a diameter of 20 micrometers . The fabrication of the integrated lightwave receiver was carried out on a nominally undoped p-type Si substrate. The p-i-n photodetector is fabricated directly on the high-resistivity substrate so that the thickness of the detector depletion layer is approximately equal to the optical absorption length of 0.8 micrometers light in silicon. A more heavily-doped p-well was formed for the NMOSFET fabrication. The silicon photodiodes have a dark current of 16 nA at 5 V, a break-down voltage of greater than 40 V, and a zero-bias capacitance of 40 fF. The external quantum efficiency of the photodiode at 870 nm is approximately 60% at 5 V without an AR coating, and the bandwidth of the device is approximately 1.5 GHz. Frequency response evaluation of the receiver indicates a bandwidth of 250 MHz with open eye diagrams demonstrated at 350 MBit/s.