As CMOS devices shrink in physical size, electrical interconnects between the devices will consume an ever-greater proportion of total chip power. A promising solution is to use silicon photonics for intra- and inter-chip communications. To be cost effective, both the optical transmitter and receiver should be made small, highly efficient, and CMOS compatible. Shrinking the photodiode will increase sensitivity and energy efficiency, but as it gets very small, the capacitance of the wire to the first amplifying stage in the receiver becomes significant. We present a solution which integrates the photodiode and first stage transistor in the form of an integrated germanium phototransistor. The rapid melt growth technique is used to integrate high quality single crystal germanium onto a silicon waveguide integrated device in a CMOS process. Bipolar gain combined with extremely compact device dimensions produces high-speeed, high-sensitivity receivers which operate at 1550 nm on a silicon photonics platform.
Project end date: 08/26/15