Broadband-Spectral-Responsivity of black silicon photodetector with high gain and sub-bandgap sensitivity by titanium hyperdoping

Abstract

Silicon, as one of the most essential semiconducting materials, is widely applied in various photodetection applications due to its high portability, convenient preparation, and compatibility with conventional complementary metal–oxide–semiconductor technology. Nowadays, black silicon, prepared by enforcing ultrafast laser micro-structuring and hyperdoping techniques, has received considerable attention for developing next-generation silicon photonics and silicon optoelectronics devices. In this work, high-comprehensive-property black silicon photodetectors with broadband spectral responsivity and high gain were achieved by femtosecond laser irradiation and titanium hyperdoping. The proposed device can respond to the incident light from 400 nm to at least 1550 nm, demonstrating a high responsivity of 40.59 A/W for 950 nm under the application of −5 V bias, and the corresponding detectivity can reach 3.61 × 1012 cm·Hz1/2W−1. Moreover, the fabricated photodetector exhibits a stable sub-bandgap photocurrent at 1550 nm, with an average responsivity of 3.42 mA/W by applying a −5 V bias. These improvements were achieved by the hyperdoping of titanium in silicon, which shows deep impurity levels, low electroactivity, and increased effective carrier lifetimes, as well as the formation of shallow n-i heterojunction and trapping centers induced by the femtosecond laser irradiation. Our work provides significant insights into the applications of black silicon in various optical-related fields, including weak and infrared photon detection, silicon photonic chips, remote sensing, and large-scale optoelectronic integration.