Sub-Bandgap Photo-Response of Chromium Hyperdoped Black Silicon Photodetector Fabricated by Femtosecond Laser Pulses

Abstract

As the main component of silicon (Si)-based Optic Electronics Integrated Circuit (OEIC) chip, Si-based infrared photodetector operating at communication wavebands is very important. In this paper, we report a kind of chromium (Cr)-hyperdoped black Si material fabricated using femtosecond laser pulses irradiation. The concentration of the Cr atoms in the black Si layer exceeds 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> and the Cr-hyperdoped Si has a large sub-bandgap absorptance (~60% for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.31 \boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> ). The deep-energy level introduced by Cr impurity is 0.39 eV below the bottom of conduction band and thus the ionized electron concentration is very low (~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> ). Owing to the excellent sub-bandgap absorption of Cr-hyperdoped Si, face-to-face black Si photodiodes are fabricated. Under illumination of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.31 \boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> light, the responsivity of the photodiodes based on N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -N junction reaches 0.57 A/W at 4.3 V bias. In addition, the rise and delay time of the device to the infrared light are on the order of milliseconds.

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