High-Sensitivity Graphene/2D Perovskite Hybrid Photodetector for Visible-Light Sensing on Silicon Nitride Photonic...

Visible-light photonic integrated circuits (PICs) with highly sensitive waveguide photodetectors (PDs) are critical to address the scaling and performance challenges in quantum information, biosensing and microscopy. While bulk materials have been employed to fabricate waveguide visible-light PDs, they face significant limitations, including complex heterogeneous integration processes and suboptimal device performance, such as high dark currents and uncharacterized on-chip sensitivity. Here, we present a strategy by exploiting the versatile integration capabilities and favorable optoelectronic properties of two-dimensional (2D) perovskite and graphene to develop a hybrid waveguide PD integrated onto a silicon nitride (SiN) platform for on-chip visible-light photodetection. By virtue of an asymmetric Schottky device structure design, the PD exhibits extremely low dark currents on the order of pA and record-high sensitivities across representative visible wavelengths (red, green, and blue), with maximum normalized photocurrent-to-dark current ratios (NPDRs) up to 10⁷ mW^-1 at a bias voltage of 1 V and a noise equivalent power (NEP) of 1.2 ± 0.4 pW Hz^-0.5. These metrics enable the detection of ultraweak light intensities as low as sub-100 pW propagating through SiN waveguides. Furthermore, we demonstrate a monolithic visible-light sensing system by integrating PDs with a SiN PIC, enabling the successful distinction of biological fluorophore-labeled DNA with a concentration difference as small as 1 μM, and an estimated detection limit to 76 nM. Our results highlight the potential of 2D material-integrated PICs for advancing scalable, high-sensitivity on-chip biosensing and other emerging visible-light applications in the future.