Colloidal Molybdenum Diselenide Nanocrystals for Tunable, Broadband, and Mixed-Dimensional Photodetectors

Two-dimensional (2D) semiconductors with a direct band gap are attractive for the fabrication of 2D/Si heterostructures for complementary metal-oxide-semiconductor compatible nanophotonic devices. We report the characteristics of sonochemically exfoliated molybdenum diselenide (MoSe2) nanocrystals (NCs) integrated on large-area Si platforms to demonstrate tunable and broadband heterojunction photodetectors. The exfoliation of bulk materials to the 2H-semiconducting phase of MoSe2 NCs exhibiting excitonic absorption peaks with characteristic 2D nature is established. A gradual blue shift in the absorption peaks accompanied by the stiffening of A(1g) Raman mode supports the size-dependent properties of NCs. Spectral response of MoSe2-NCs/Si (2D/3D) heterojunction devices reveal size-tunable and broadband (400-1400 nm) photoresponse, with the optimum sample (size similar to 12 nm) showing a peak responsivity and a detectivity of similar to 960 mA/W and similar to 1.8 x 10(12) Jones, respectively, at a low bias (-2 V).

Automated summary

The study focuses on the characteristics of sonochemically exfoliated molybdenum diselenide nanocrystals integrated on large-area silicon platforms to demonstrate tunable and broadband heterojunction photodetectors. The research established the excitonic absorption peaks with characteristic 2D nature in the 2H-semiconducting phase of MoSe2 nanocrystals. The spectral response of MoSe2 nanocrystals/Si heterojunction devices reveals size-tunable and broadband photoresponse.