transition metal dichalcogenides (TMDs) have caught much interest due to their applications in various fields like optoelectronics, [1] sensors, [2] strain engineering, [3,4] valleytronics, [5] spintronics, [6] etc. 2D materials because of its reduced dimension experience reduced dielectric screening. [7,8] The electric field lines between an electron and hole in a single layer of a 2D material extend above and below the surface, with no material available to screen the field lines. [9] This results in a large exciton binding energy [7,8,[10][11][12][13] as well as increased quasiparticle band gap [14] and make the electrical and optical properties of the material susceptible to its dielectric environment. [15,16] A dielectric environment modifies the electron-hole interactions in 2D materials and helps in controlling the band gap of 2D materials [14,17] without disturbing the pristine quality of these materials. Previous theoretical and experimental studies have shown that a higher dielectric environment could reduce the fundamental band gap and exciton binding energy in 2D materials. [13,15,[18][19][20][21][22] The dielectric environment also plays a crucial role in determining the impurity scattering of charge carriers in 2D materials. [23][24][25] This effect is primarily responsible for the enhanced mobility of 2D materials in high dielectric medium. [23,24] Depending on the dielectric mismatch between the 2D semiconducting materials and the surrounding dielectric environment, the effective potential experienced by a mobile electron due to an ionized impurity at the surface of the membrane enhances or diminishes. [23] This effect also depends on the thickness of the semiconducting membrane. When the thickness increases above a critical limit, dielectric mismatch has no effect on Coulomb scattering. [23] All these effects show that controlling the dielectric environment of 2D materials is particularly interesting because of its profound impact on the electronic band gap, screening, exciton and trion binding energies, exciton transport, and mobility modulation, which can help toward the efficient design of various optoelectronic devices.Even though research on 2D TMDs is growing faster with the discovery of more exciting properties, its production and application have not yet started at an industrial scale. So, it isThe reduced dielectric screening in the out of plane direction, makes 2D materials sensitive to the surrounding environment, offering a unique platform with greatly tunable optoelectronic properties. Large exciton binding energy in 2D materials limits their photogeneration efficiency. The strong electric field generated at a p-n junction will help in separating these strongly bound electron hole pairs. Here, the present study demonstrates how engineering the surrounding dielectric environment would facilitate a mixed dimensional van der Waals p-n junction to improve the photoresponse to a great extent. A 3D silicon-2D monolayer MoS 2 heterostructure is fabricated as a model system. Nearly three ord...

Heterostructures based on two-dimensional (2D) materials have demonstrated huge potential in various modern-day electronic and optoelectronic devices, but their optoelectronic properties are strongly influenced by the defects present in these materials. Hence, an in-depth understanding of the role of defects is vital in designing high-performance optoelectronic devices. Here, we investigated the role of defects in the electronic transport and photoresponse properties of a silicon−MoS 2 p−n junction heterostructure through temperature-dependent electrical studies and demonstrated a method for improving their photoresponse. The presence of space-charge-limited transport with exponentially distributed trap states was evident from the temperature-dependent I−V characteristics. The temperature dependence of the ideality factor and intensity-dependent photoresponse also elucidated the nature of defects. The amplitude of low-frequency 1/f noise was observed to decrease with an increase in temperature, revealing the significant influence of defects on the charge transport. These defects can often cause recombinations, diminishing the photoresponse and severely degrading the optoelectronic properties. A significant enhancement in photoresponse by reducing the recombination centers was obtained by altering the surrounding dielectric environment. For a particular dielectric, the enhancement was observed to be more prominent toward low temperatures. In addition, the surrounding dielectric also effectively suppressed the low-frequency noise levels in the heterostructure. Insights from this study would help in designing and improving the properties of low-dimensional optoelectronic devices.

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