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 SiO 2 (SiQDs:SiO 2 ) 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:SiO 2 (p-SiQDs:SiO 2 ) heterojunction photodetectors (PDs) by using graphene quantum dots (GQDs) as an interlayer. The TFSA-GR/p-SiQDs:SiO 2 /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:SiO 2 , 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 (∼10 6 and 4.50−8.35 × 10 12 cm Hz 1/2 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.

Two-Dimensional Nanocrystal Assemblies for Photocapacitive Devices

“…Here, we describe the emergence of photocapacitance in two-dimensional (2D) nanocrystal (NC) assemblies. Recent studies have highlighted the potential of NCs in photodetection − and sensing particularly when hybridized with 2D layered materials such as graphene and MoS 2 . − Indeed, NC–graphene hybrid devices have been shown to achieve on-device gain in excess of 10 8 per photon. ,− …”