Si compatible MoO3/MoS2 core-shell quantum dots for wavelength tunable photodetection in wide visible range

Abstract

Silicon compatible, wafer scale MoO3/MoS2/Si heterojunctions for wavelength selective photodetection applications in the spectral range of 400–700 nm using variable size MoS2 colloidal quantum dots (QDs) and the oxide shell to core thickness ratio, has been reported. It is found that a very controlled oxidation occurs in the MoS2 colloidal QDs under the ambient condition giving rise to oxide/MoS2 core-shell structure. The oxide shell has exhibited an amorphous nature of MoO3, while the core has maintained the high crystalline quality of MoS2. Wavelength tunable photodetection is reported using the core-shell QDs with varying size of 70 to 4 nm. The responsivity and detectivity characteristics peak at ~400 nm for QDs of size ~70 nm and these peaks shift to ~650 nm with scaling down of QD size. A mixed current conduction mechanism is observed across MoO3/MoS2/Si heterojunction, which is partly ohmic in nature and partially trap-charge-limited. A dark current as low as 1.66 × 10−8 A at −3 V and a photo-to-dark current ratio of ~116 have been achieved. The peak responsivity and detectivity of the core-shell heterojunction detectors are estimated to be ~0.16 A/W and ~2.8 × 1011 Jones at −3 V.