Design and analysis of Si-Ag-graphene-HfO2 heterojunction based ultraviolet photodetector

This study reports on Si-Ag-Graphene ultraviolet (UV) photodetector (PD) design under zero bias while analyzing the role of varying thicknesses of antireflection HfO2 layers. The performance of the proposed PD is analyzed using the FDTD (finite difference time domain) solver, while considering the condition of normal incidence of radiation. The simulation findings reveal that for Si-Ag-Graphene PD design, a coating of 10 nm-thick HfO2 layer is beneficial to attain higher magnitudes of quantum efficiency (eta) and responsivity (rho). The Si-Ag-Graphene-HfO2 (10 nm) PD design exhibits a maximum magnitude of eta = 0.63 and rho = 0.15 A/W at an operating wavelength (lambda(0)) of 294.7 nm. Additionally, at lambda(0) = 294.7, the device shows an impressive UV-to-visible rejection ratio (rho(294)/rho(550)) of 36.58.Also, this PD design, around lambda(0) similar to 232 nm, shows a maximum photocurrent (I-p) of 3.5 mA. Further, the electrical performance of the Si-Ag-Graphene-HfO2 (10 nm) PD design is analyzed to evaluate the dark current (I-d), detectivity (D*), and minimum detectable power (P-d) for the possible practical implementation of the proposed PD structure. With an applied bias of -1.5 V to 1.5 V, the Si-Ag-Graphene-HfO2 (10 nm) PD design exhibits an I-d of 7.09 x 10(-21)A, D* of 0.94 x 10(12) Jones, and P-d value of 4.73 x 10(-20) W at 0V. This Si-Ag-Graphene-HfO2 (10 nm) PD design possesses exceptionally large magnitudes of absorbance with superior rho and D* compared to the current state-of-the-art. The proposed DUV PD can find applications in various high-end fields such as microelectronics and solar missions etc.