|M.Sc Student||Kraus Shraga|
|Subject||An InP-Based Optoelectronic Integrated Circuit for Optical|
|Department||Department of Electrical Engineering||Supervisor||Professor Dan Ritter|
Heterojunction Bipolar transistors (HBTs) based upon the Indium Phosphide material-system exhibit cutoff frequencies in excess of 200 GHz. The same semiconductor material-system also serves for the fabrication of photodiodes for optical communication at 1.55 um. Thus, InP-based HBTs may play an important role in fiber optic communication system operating at rate of 40 Gbps and beyond. In order to achieve this demanding goal monolithic photoreceiver front-ends are required, coupled with state-of-the-art technology.
This work discusses the design, fabrication, and measurement of InP-based optoelectronic integrated circuits. We focus on photoreceiver front-ends that consist of a photodiode and a transimpedance amplifier. Two types of amplifiers were studied: lumped and distributed. The former type excels in small area, low power consumption, and low noise, whilst the latter exhibits considerably higher bandwidth using the same transistors. The lumped amplifiers were designed as transimpedance feedback amplifiers. The main challenge in the design of the traveling wave amplifiers was to reduce their input impedance. The amplifiers were characterized electrically up to 67 GHz, and the monolithic receiver chips up to 40 GHz. The lumped circuits exhibited electrical bandwidth of 22 GHz input resistance of 12 ohm. The distributed circuits had an electrical bandwidth of 60 GHz and input resistance of 25 ohm. The optical bandwidth of the receiver was limited by the transit time of the photodiode: 14.2 GHz for the lumped receiver and 20.2 GHz for the distributed receiver. Work is in progress to reduce the photodiode transit time in order to obtain an optoelectronic bandwidth comparable to the electric bandwidth.