Research Projects

Polarization-sensitive broadband photodetectors have gained significant interest because of their many applications in fields like military investigation, astronomy, multichannel optical communication, environmental monitoring, and night vision camera. The conventional broadband and infrared detectors are typically based on bulky III-V compound semiconductors or other narrow-bandgap materials, such as Si (0.2-1100 nm) InSb (3000–6000 nm), Hg₁₋ₓCdₓTe (6000–15000 nm), and In₁₋ₓGaₓAs (sensitive to 1000–3000 nm), each of which operates within particular visible to IR wavelength ranges. Despite their effectiveness, these technologies have several significant disadvantages, including complicated manufacturing processes, a requirement for cryogenic temperatures to function successfully, and difficulty integrating with existing silicon-based technologies. Additionally, external optical components like polarizers and waveplates are frequently used to accomplish polarization detection, which adds bulk and restricts the practical applications of these systems. Two-dimensional (2D) materials have exciting properties, which include tunable band gap, strong-light matter interaction, high carrier mobility, flexible electronics, and more exotic properties, which make them promising candidates for overcoming the limitations of conventional infrared photodetectors. Materials like black phosphorus (BP) and b-AsP, known for their infrared absorption and inherent anisotropy, were among the first 2D systems to demonstrate a polarization-dependent photoresponse. However, its poor ambient stability hinders its practical applications. Hence, there is a high demand to fabricate high-performance, stable, scalable and high-polarization-sensitive photodetectors that can work at room temperature. Other 2D materials such as ReSe2, ReS2, GeS2, and GeSe2 have shown polarization detection ability, but their low anisotropic ratio and slow response time remain key challenges to overcome. Interestingly, Palladium diselenide (PdSe2) with strong in-plane anisotropy (due to puckered pentagonal structure), high ambient air-stability, high carrier mobility and widely tunable bandgap (0.03-1.3 eV) is the best suitable candidate for synthesizing highly sensitive polarization photodetector. Still, the high dark current (due to its narrow band gap) and limited on-off ratio in PdSe2 are a few bottlenecks. To address the above shortcomings, the fabrication of its van der Waals heterostructure with a suitable candidate is the best approach. A heterojunction is an interface of two different materials with altogether different properties. Thus, by using a heterojunction, we can utilize the advantages of both materials, leading to an increased device capability as compared to individual materials. WSe2 is another 2D material with band gap range of 1.25 eV-1.6 eV, high absorption coefficient and ambient stability is best suited material for heterostructure fabrication. Therefore, our main goal is to design PdSe2/WSe2 heterostructure with detailed interface study and charge transport mechanism to develop high polarization sensitive IR photodetector that can work at ambient conditions. To confirm the polarization (or anisotropic) nature of the heterostructure variations characterizations measurements such as angle-resolved polarized Raman spectroscopy (ARPRS) and Azimuth dependent reflectance difference microscopy (ADRDM) will be performed. Furthermore, a detail interface study using x-ray photoelectron spectroscopy (XPS), Ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe force microscopy (KPFM) also be carried. To uncover the underlying mechanisms in the PdSe2/WSe2 heterostructure, theoretical calculations will be employed to analyze electronic and optical spectral features. These simulations will directly support and validate experimental observations, offering a deeper understanding of interface physics and optical anisotropy.