Resonant nanocavity-enhanced graphene photodetectors on reflecting silicon-on-insulator wafers

The weak light absorption and zero-bandgap properties of two-dimensional graphene negatively affect electron–hole recombination and quantum yield, restricting its usefulness in practical optoelectronic applications. In this work, plasma-assisted chemical vapor deposition is used to synthesize three-dimensional graphene (3D-graphene) in situ on the surface of silicon-on-insulator (SOI) wafers, thereby creating high-performance broadband photodetectors. The nanocavity structure of the 3D-graphene integrates with the optical cavity structure of the SOI to enhance the interaction that occurs between the 3D-graphene and incident light. The resulting device has excellent performance in the near-infrared (NIR). The mechanism by which the light absorption of the photodetector is enhanced is explored in detail via experimental analysis and theoretical calculation. Photodetectors based on the 3D-graphene/SOI Schottky heterojunction exhibit a broad detection range (from 440 to 1550 nm), ultrahigh responsivity (27.4 A/W), and excellent detectivity (1.37 × 1011 Jones) at a wavelength of 1550 nm. The Schottky heterojunctions combine two structures (nanocavity and optical cavity) that enhance light absorption. They are also compatible with complementary metal-oxide-semiconductor technology, providing a strategy for manufacturing high-performance NIR photodetectors.