CMOS PIN Phototransistors for High-Speed Photosensitive Applications

AbstractThis work reports on two 40×40μm2 high-speed pnp phototransistors built in a standard 0.18μm CMOS process without modifications. The phototransistors were implanted on wafer consisting of a p+ bulk with a p− epitaxial layer on top of it. Bandwidths up to 50MHz and a gain in responsivity of more than a factor of 3 at 850nm light compared to the photodetector presented in [1] are achieved. Due to the achieved measurements, these phototransistors are well suited for high speed photosensitive applications where inherent amplification is needed like light barriers, image sensors, high speed opto-couplers, etc