Photodiode with micro texture for improving sensitivity at large angle of incidence for particle sensors

This paper reports on a photodiode (PD) with micro texture for miniaturizing particle sensors. We proposed an optical system for a small particle-sensor without focus lenses. The system requires a PD which is high sensitive at large angle of incidence. The micro texture was fabricated on a surface of the PD to achieve the required property. The micro texture was an array of columnar-like structures that had a part of inverse-tapered shape. The all surface of the structures was n-type doped layer. Experimental results show that the sensitivity of the PD with micro texture increased with an increase in the incident angle. Furthermore, we demonstrated that the proposed optical system using the PD detected light scattered from smoke of an incense stick. Hence, the PD is suitable for realizing small particle-sensors.