Simulation and Analysis of GaAs‐Au Layer‐HfO2 Dual‐Band Photodetector with High Performance in Visible Spectral Region

Abstract This study presents a dual‐band GaAs‐Au layer‐HfO 2 heterojunction‐based photodetector (PD) designed for visible spectral range. The optical response of the proposed PD design, operating under zero‐bias conditions, is comprehensively investigated using finite difference time domain (FDTD) simulations in the whole visible region (360–700 nm). The results indicate that a 10 nm Au layer in combination with a 20 nm HfO₂ layer leads to superior optical performance. Under zero‐bias conditions, the proposed design GaAs (1000 nm)‐Au layer (10 nm)‐HfO₂ (20 nm) exhibits high absorbance (A) = 0.952 a.u., quantum efficiency (η) = 0.585, and responsivity (ρ) = 299 mA W −1 at wavelength (λ) = 636.17 nm in the red band. The same design provides A = 0.808 a.u., η = 0.446, and ρ = 182 mA W −1 at λ = 506.78 nm in the green band. Further, an electrical simulation of the PD design, i.e., GaAs (1000 nm)‐Au layer (10 nm)‐HfO₂ (20 nm)–ZnO (10 nm) exhibits an ultra‐low dark current (I dark ) of 1.64 × 10 −12 A, and the corresponding detectivity (D * ) of 0.15 × 10 9 Jones in green band, and 0.26 × 10 9 Jones in red band under zero‐bias condition. These results further establish that that the proposed PD design is capable of providing superior performance compared to several recently‐reported visible region PDs. The proposed PD design with dual‐band performance provides a crucial versatility as the same design can efficiently operate across two separate spectral ranges. This capability is especially beneficial for diverse optical sensing applications that demand high sensitivity across multiple wavelength ranges.