Enhanced Broadband Photodetection with Geometry and Interface Engineered Nanocrystalline Graphite

Abstract

AbstractPhotodetection across the near‐infrared (NIR) to short‐wavelength infrared (SWIR) spectrum is important for many applications. This study explores photodetection using nanocrystalline graphite (NCG) in a suspended, narrow constriction configuration for improved performance. Bowtie constrictions are fabricated in both suspended and substrate‐supported NCG devices, allowing for accurate comparison. It shows that the suspended constriction enhances the bolometric photoresponse and sensor detectivity by several orders of magnitude compared to the substrate‐supported counterparts, attributed to reduced thermalization and electric field concentration. The suspended configuration preserves a spectrally flat photoresponse while reducing operating voltage through a tailored NCG layer thickness. Chromatic aberration‐corrected photocurrent spectroscopy is used to measure the photoresponse from 1100 to 1700 nm, and diffraction‐limited hyperspectral photocurrent imaging is conducted to measure the local photocurrent generation across the device. Bolometric and photo‐thermoelectric currents are restricted to the suspended central constriction due to electric field concentration and thermal decoupling and the direction of the photocurrents within the sensor is revealed. The experimental data is complemented by simulations of the light absorption and the electric field distribution. This work indicates the importance of geometry and thermal decoupling for boosting device performance, offering promising prospects for sensitive and low‐power NCG‐based photodetectors in the NIR‐SWIR range.