On-Chip Ge Photodetector Efficiency Enhancement by Local Laser-Induced Crystallization

Metal-semiconductor-metal plasmonic nanostructures enable both on-chip efficient manipulation and ultrafast photodetection of strongly confined modes by enhancing local electrostatic and optical fields. The latter is achieved by making use of nanostructured thin-film germanium (Ge) plasmonic-waveguide photodetectors. While their sizes and locations can be accurately controlled during the nanofabrication, the detector efficiencies are significantly reduced due to deposited Ge amorphous nature. We demonstrate that the efficiency of waveguideintegrated Ge plasmonic photodetectors can be increased significantly (more than 2 orders of magnitude) by spatially controlled laser-induced Ge crystallization. We investigate both free-space and waveguideintegrated Ge photodetectors subjected to 800 nm laser treatment, monitoring the degree of crystallization with Raman spectroscopy, and demonstrate the efficiency enhancement by detecting the telecom radiation. The demonstrated local postprocessing technique can be utilized in various nanophotonic devices for efficient and ultrafast on-chip radiation monitoring and detection, offering significantly improved detector characteristics without jeopardizing the performance of other components.

Automated summary

Metal-semiconductor-metal plasmonic nanostructures enhance on-chip manipulation and ultrafast photodetection by improving local fields. By using laser-induced Ge crystallization, efficiency of Ge plasmonic photodetectors can be increased significantly. This local postprocessing technique can be used in various nanophotonic devices for efficient on-chip radiation monitoring and detection.