Deep-Ultraviolet Photodetectors Based on Hexagonal Boron Nitride Nanosheets Enhanced by Localized Surface Plasmon Resonance in Al Nanoparticles

Hexagonal boron nitride (h-BN), a two-dimensional-layered material, exhibits the outstanding properties of ultrawide band gap, high absorption coefficient, and high chemical and thermal stability. Because of these appealing properties, h-BN has emerged as a suitable material for the fabrication of deep-ultraviolet (UV) photodetectors (PDs). We demonstrate plasmonic-enhanced deep-UV PDs based on h-BN nanosheets by utilizing localized surface plasmon resonance in Al nanoparticles (NPs) in the deep-UV region. Using a cost-effective and efficient method of dewetting, different sizes of NPs are deposited on h-BN layers, and their effect on PDs is investigated. Upon performing a detailed set of photoelectrical measurements, we establish that the presence of NPs leads to a significant enhancement in the illumination current and related performance parameters of the PDs. By using an extremely low value of the incident optical power density of 2.5 μW cm^-2, a significant enhancement by 5.5 times is observed in the current at a deep-UV wavelength of 205 nm. Moreover, at a low input voltage of 1 V, the responsivity improves by ∼60%, without degrading the UV-visible rejection ratio of the PDs. The mechanism behind the enhancement is investigated in detail by numerical simulation of the absorbance spectra and electric field intensity distributions of the Al NPs. Furthermore, even after surface modification of h-BN, the speed of the PDs remains almost unaffected, thereby establishing the effectiveness of the approach used to improve the PDs.