Intact Vertical 3D–0D–2D Carbon‐Based p–n Junctions for Use in High‐Performance Photodetectors

Abstract Ultrathin 2D graphene (2D‐Gr) sheets have inherently weak absorption characteristics (only 2.3%). Pristine‐graphene‐based photodetectors therefore have short carrier lifetimes and small Schottky barriers that severely restrict their practical application. In this work, chemical vapor deposition (CVD) and dynamic plasma‐assisted CVD (PACVD) are used to grow vertical p–n junctions in situ, which can then be used to form novel near‐infrared photodetectors. The directly formed vertical heterostructures feature 0D C₃N quantum dots (QDs) in the middle position which acts as nucleation seeds to directly and rapidly grow 3D graphene (3D‐Gr) structures that act as the n‐type region. The bottom layer consists of a single‐crystal 2D‐Gr film that forms the p‐type region. The large built‐in electric field at the interface of the depletion region of the 3D‐Gr/2D‐Gr vertical p–n junction leads to the rapid separation of any photogenerated electron–hole pairs. Thus, the photodetector exhibits an excellent responsivity of 2.98 × 10⁷ A W⁻¹ and a detectivity of 1.04 × 10¹³ cm Hz^1/2 W⁻¹ at a wavelength of 1550 nm. The response speed of the photodetector is ultrafast and exceeds that of other vertical/lateral p–n‐junction‐based photodetectors. Its speed is ascribed to the synergism that exists between the C₃N QDs and 3D‐Gr due to their unique electron distributions and structural distortions. The research paves the way for a novel class of high‐performance graphene‐based photodetectors with hybrid architecture.