Bandwidth Limitation of Directly Contacted Graphene–Silicon Optoelectronics

Electrically contacting layered materials on a complementary metal-oxide-semiconductor transistor (CMOS)-processed lateral silicon homojunction offers a new platform enabling postfabrication-free high-speed hybrid optoelectronic devices on chip. Understanding detailed junction formation and radiofrequency (RF) response on the multicomponent interface between directly contacted silicon nanophotonic devices and low-bandgap materials is essential for predicting the performance of those active components. Electrostatic carrier distribution as well as the dynamics of externally injected carriers are strongly influenced by spatially varying Schottky barriers on the vertical heterojunctions. In this work, we analyze the high-speed RF response of a graphene “bonded” lateral silicon p-i-n junction. The multijunction structure on the hybrid structure is parametrized by fitting a small-signal model to the broadband coherent radio frequency response of the hybrid device at a series of different carrier injection rates. By engineering the device dimensions, it is possible to suppress the resistance–capacitance delay to be less than a picosecond and enable sub-terahertz bandwidth operation.