A traveling-wave model for optimizing the bandwidth of p-i-nphotodetectors in silicon-on-insulator technology

摘要

The paper presents an efficient design method for predicting thenbandwidth of traveling-wave photodetectors (TWPD's) innsilicon-on-insulator (SOI) coplanar technology. First thentransmission-line parameters describing the propagation mechanism in thenstructure are computed up to optical frequencies, as a function of thengeometry and of the carrier concentrations. Next, a traveling-wavenequivalent model is derived, which takes into account the propagationnmechanism of the optical beam into the silicon active area and thencarriers transit time in the p-i-n junction. Using the model enables usnto theoretically optimize the radio-frequency output power of the p-i-nnstructure over a wide frequency range by a judicious choice of thenoptical and RF loads at the accesses of the equivalent opto-electronicncoupler formed by the TWPD. SOI coplanar TWPD's supporting a travelingnoptical wave exhibit an improvement of the 3-dB bandwidth by more thann50% compared with uniformly illuminated SOI PD's or with GaAs TWPD's ofnsame geometry and the bandwidth-efficiency product can be enhanced bynachieving adequate reflection conditions for the optical signal at thenends of the SOI device