ABSTRACT
A one-chip p-i-n/FET circuit for 155Mbps local loop application is designed and fabricated. We make emphasis on dynamic range rather than on sensitivity, and on low fabrication cost rather than on high performance, for this application. A new noise analysis technique is used to optimize the circuit. A p-i-n photodiode integrated with a simple source follower circuit consisting of one JFET, one channel resistor, and one NiCr resistor provides a bandwidth of 120MHz, a transimpedance of 1kΩ at 50Ω load, a sensitivity of -34.2dBm and a dynamic range of 34dB. An MOCVD technique is used to grow the whole epi structure without interruption. The InP/InGaAs photodiode layers are stacked on top of the FET layers and the highly doped channel layer of the FET is also the n+ layer for the photodiode. Zn and Cd diffusion processes are used in the simultaneous formation of p-type layers for both photodiode and the junction FET (JFET).
