Remarkable Noise Reduction in High-Stability Self-Powered Doped Graphene/Si-Quantum Dot Broadband Photodetectors by Using Graphene Quantum Dots as an Interlayer

Abstract

Si quantum dots (SiQDs)-embedded SiO2 (SiQDs:SiO2) is highly attractive for photonic device applications due to advantages such as larger light absorption and faster photo-sensing than bulk Si. Here, we report (trifluoromethanesulfonyl)-amide (TFSA)-doped graphene (GR) (TFSA-GR)/p-type SiQDs:SiO2 (p-SiQDs:SiO2) heterojunction photodetectors (PDs) by using graphene quantum dots (GQDs) as an interlayer. The TFSA-GR/p-SiQDs:SiO2/n-Si PD exhibits a broadband photoresponse even at zero bias, meaning “self-powered”, with a 0.36–0.67 A W–1 responsivity and an ∼90% external quantum efficiency in the 400–1000 nm wavelength range. By inserting GQDs as an interlayer between the TFSA-GR and p-SiQDs:SiO2, the PD shows a remarkable reduction in dark current (DC) due to the carrier blocking effect, resulting in an ∼100 times’ increase of the photocurrent (PC)/DC ratio and detectivity (∼106 and 4.50–8.35 × 1012 cm Hz1/2 W–1), respectively. The PC rise/decay times are also reduced to ∼1.08/0.94 μs from 1.22/1.46 μs at 600 nm, respectively, by the interlayer. The PC/DC is almost consistent even after 1000 h under ambient conditions (25 °C temperature/30–35% relative humidity), indicating excellent stability.