Fabrication and characterization of photodiodes for silicon nanowire applications and backside illumination

Although silicon photodetectors are widely used in the manufacture of consumer cameras and light sensors, their fabrication requires a large number of process steps, equipment and resources. In order to study novel device concepts, such as the inclusion of silicon nanowires, quantum-confinement, nanostructured moth-eye structures or on-chip optical filtering, we need control over critical fabrication steps, which is not possible if we rely only on commercially produced devices. In this work, we have designed, fabricated and characterized silicon photodiodes starting from bare silicon wafers to completely packaged chips. We considered two major configurations--front-side illuminated detectors on standard SSP silicon wafers, and back-side illuminated detectors with ultrathin DSP silicon wafers. Ion implantation process was used for creating the p-n junctions, but we also acquired a diffusion furnace and developed our own process for thermal diffusion from a solid source. We also fabricated silicon nanowires on the front side of the diodes using a gold metal-assisted chemical etching (MACE) process to examine their effects on the optical and electrical performances of the devices. The fabricated devices were tested on a probe station, and then they were packaged, wire-bonded and tested for optical responsivities and quantum efficiencies