Self-aligned on-chip coupled photonic devices using individual cadmium sulfide nanobelts

Nanowires (NWs) and nanobelts (NBs) have been widely studied and fabricated into a variety of nanoscale devices such as light emitting diodes (LEDs), lasers and biosensors. These unique materials have attracted sustained attention due to their novel properties, ease of growth, and the ability to fabricate highly engineered devices. However, their widespread application remains hindered due to the difficulty in integrating multiple NWs or NBs together for more complex devices. Integration of multiple NWs and NBs together on the same chip can enable the coupling of different devices to help realize complex on-chip architectures such as photonic integrated circuits or nanoscale diagnostic tools, which currently require outcoupling using larger components. In this letter we report the coupling of on-chip NB LEDs and photodetectors using a single, precisely self-aligned, cadmium sulfide (CdS) NB fabricated on a silicon-on-insulator (SOI) substrate. Electroluminescence generated by the CdS NB is waveguided and measured across the self-aligned device and demonstrates an on/off ratio of 10²-10³. This work describes a new method for fabricating and integrating more complex nanoscale devices that can enable advances in areas such as on-chip optical computational components and nanoscale optical biodiagnostics.