Enhanced efficiency of high-speed Si and Si-based PbSe MSM photodiodes with integrated photon-trapping holes in 800 ~ 1550 nm wavelengths

We demonstrate theoretically and experimentally that cylindrical-shaped hole array with a small depth and an appropriate period integrated on SOI substrate can enhance infrared absorption due to more bending of light and a higher back reflection. Si MSM photodiode with hole array with a depth of 250 nm exhibits a 3-fold improved EQE of 61%, and an ultrafast impulse response speed of 22 ps enabling a 3dB bandwidth up to 23.9 GHz. PbSe film with a thickness of 80 nm is integrated to broaden the response wavelength. More than 500% EQE enhancement of the Si-based PbSe photodiode with 150-nm-deep photon-trapping holes is achieved at 1550 nm compared to the device without hole structures. These photodiodes offer the potential to drastically improve the efficiency and bandwidth of Si-based detectors in wide band and reduce the cost of infrared sensing and communication system.