Broadband infrared photodetector based on nanostructured MoSe₂–Si heterojunction extended up to 2.5 μm spectral range

Abstract

Transition metal dichalcogenides (TMDs) and their heterojunctions are drawing immense research interest for various applications including infrared detection. They are being studied with different semiconductor materials to explore their heterojunction properties. In this regard, we report a MoSe2/Si heterojunction broadband photodiode which is highly sensitive for a wide spectral range from 405 nm to 2500 nm wavelength with the maximum responsivity of ∼522 mA W−1 for 1100 nm of incident light. The hydrothermal synthesis approach leads to the imperfect growth of the MoSe2, creating defects in the lattice, which was confirmed by x-ray photo-spectroscopy. These sub-bandgap defects caused high optical absorption of the SWIR light as observed in the absorption spectra. The speed of the device ranges to 18/10 μs for 10 kHz modulated light. Furthermore, the photodetector has been fully operational even at zero bias voltage, making it a potential contender for self-powered photodetection.

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

“…At 514 nm, the LDR of the MoSe 2 (∼12 nm)/Si photodetector is estimated to be ∼69 dB with an optical illumination density of 12.7 mW/cm 2 (−2 V). The performance of similar 2D/Si heterojunction devices reported in the literature has been compared and summarized in Table . ,,,− The variation of external quantum efficiency (EQE) is shown in Figure S7, and the maximum EQE value is found to be around 165% at ∼600 nm for the MoSe 2 -NC (∼12 nm)/Si device, indicating a photoconductive gain in NC heterojunction devices. The charge transfer mechanism of the device can be explained using the energy band alignment, and the schematic representation of band edges for the Au/ n -MoSe 2 /p-Si/Al device is presented in Figure a, with their respective energy values taken from existing reports. , In equilibrium, the band alignment (flat-band condition) is shown in Figure b, where the values of conduction band offset and valence band offset for the heterojunction are found to be ∼0.48 and ∼0.89 eV, respectively.…”

“…Molybdenum diselenide (MoSe 2 ), less popular among TMDs, has a triatomic layer structure where a layer of Mo atoms covalently sandwiched between two selenium (Se) atomic layers (Se–Mo–Se) and each unit is stacked vertically by van der Waals bonding to form the bulk crystal. , It shows a hexagonal symmetry such as the graphene sheet in 2D projection with a direct optical band gap of ∼1.6 eV in a monolayer form while its bulk band gap being indirect (∼1.2 eV) . Broad spectral selectivity, stability, and high absorptivity make 2D MoSe 2 very much attractive for optoelectronic devices such as photodiode and phototransistors. − There have been tremendous advancements in different synthesis methods to produce high-quality MoSe 2 including mechanical exfoliation, chemical exfoliation, chemical vapor deposition (CVD), and so forth. − Though mechanically exfoliated flakes exhibit excellent optical characteristics, the nanolithography process needs to be employed for fabricating devices, making the process costly and incompatible to batch processing. , …”

Filterless Discrimination of Wavelengths in the Range from Ultraviolet to Near-Infrared Light Using Two PdSe2/Thin Si/PdSe2 Heterojunction Photodetectors

“…However, the absorption coefficient at 1200 nm will decrease to 2.20 × 10 –2 /cm, nearly eight orders of magnitude lower than that in the deep ultraviolet region. On this account, when the thin Si wafer was chosen to assemble the heterojunction photodetector, the as-formed device displayed rather different optoelectronic characteristics, in that the wavelength-dependent light absorption coefficient caused insufficient absorption of near-infrared (NIR) or even visible light, compared with the bulk Si. − Further careful examination of the I – V curve in the inset of Figure e shows that the current heterojunction actually exhibits a weak photovoltaic behavior, which is probably owning to the difference in the width of the built-in electric field between both PdSe 2 /thin Si heterojunctions. As a result, the asymmetric electric potential distribution in Si could lead to the formation of two Schottky junctions with different barrier heights upon light illumination. , When illuminated by 680 nm light, the PdSe 2 /thin Si/PdSe 2 heterojunction will show pronounced photoresponse (Figure e).…”

Recent progress in optoelectronic applications of hybrid 2D/3D silicon-based heterostructures

“…In addition, the response speed approaches 0.12 μs, meaning the device may be used in high-speed circuits. Almost the same time, John et al [83] fabricated a MoSe 2 /Si p-n junction photodiode whose spectral range covered 405 to 2500 nm, and the maximum responsivity of 522 mA W −1 was attained at the illumination of 1100 nm incident light. The MoSe 2 nanosheets were synthesized by a hydrothermal method, causing many defects in the lattice which was the main reason for high optical absorption of the shortwave infrared light.…”