CMOS-MEMS Photovoltaic Energy Harvester with an S-Shaped Diffusion Structure

This work presents a complementary metal oxide semiconductor (CMOS)-compatible photovoltaic energy harvester (PVEH) incorporating an S-shaped diffusion architecture for optical energy harvesting. The device is implemented using the CMOS process with an effective photovoltaic active area of 1 mm2. The structure employs an S-shaped p-type diffusion within the n-well together with closely spaced n-type diffusion regions to establish a compact photoactive region for photogenerated carrier collection. Three-dimensional TCAD simulations were performed to investigate the photovoltaic characteristics under irradiance levels ranging from 200 to 1000 W/m2. A post-CMOS process was subsequently employed to remove the dielectric layer above the photoactive region and provide optical access to the semiconductor surface. At 1000 W/m2, the fabricated PVEH exhibited an open-circuit voltage of 0.5 V, a short-circuit current of 405 μA, and a maximum output power of 137 μW, corresponding to an energy-conversion efficiency of 13.7%. These results demonstrate the feasibility of implementing the S-shaped diffusion architecture using standard CMOS technology and post-CMOS processing, providing a compact photovoltaic energy harvesting solution for low power sensors and self-powered microsystems.