MXene-Based Double-Layer Side-Illuminated Photodetector: A Theoretical Investigation with Comparative Analysis to Graphene-Based Devices

This comprehensive theoretical study investigates a novel MXene-based side-illuminated Schottky photodetector (SIMS-PD) integrated on an InP waveguide platform for telecommunication wavelengths. Building on our previous work with graphene-based devices achieving responsivities up to 1.76 A/W, we propose a Ti₃C₂Tₓ MXene double-layer structure that theoretically demonstrates superior performance metrics. Through electromagnetic modeling using Lumerical MODE and COMSOL Multiphysics, we predict a responsivity of 2.31 A/W at 1.55 μm—representing a 31% improvement over trilayer graphene devices. The MXene structure exhibits ultra-low dark current (5×10⁻¹⁶ A), exceptional detectivity (2.1×10¹³ Jones), and 42 GHz bandwidth capability. These enhanced properties arise from MXene’s unique combination of metallic conductivity (8,500 S/cm), tunable work function (4.1-4.8 eV), and strong optical absorption coefficient (3.8×10⁵ cm⁻¹). Comparative analysis reveals MXene’s advantages in terms of solution processability, environmental stability, and voltage tunability (Δμ = 0.8 eV) over graphene counterparts. The proposed device architecture features optimized field confinement at the MXene-InP interface with 85% modal overlap, achieving quantum efficiency of 0.69. This work establishes MXene as a promising alternative to graphene for next-generation integrated photodetectors, particularly for applications in optical communications, quantum technologies, and high-sensitivity sensing systems.