3rd TAGRA

Metal-semiconductor-metal (MSM) photodetectors are strong candidates for high-speed optical receivers and ultraviolet sensing owing to their planar structure, single-step lithographic fabrication, low capacitance and compatibility with field-effect transistor technology. However, MSM performance depends not only on the absorber material but also on the electrode geometry and the physics of the metal-semiconductor interface. Reducing the finger spacing increases speed but also increases shadowing, while raising the Schottky barrier height suppresses dark current. These competing effects turn device design into a multi-parameter optimization problem and make experimental exploration costly. In this work, MSM photodetectors are modeled in SCAPS-1D as an equivalent one-dimensional structure consisting of two back-to-back Schottky contacts. The Poisson, continuity and drift-diffusion equations are solved together with the Shockley-Read-Hall recombination model at 300 K, and the model is validated against experimental results reported in the literature. Absorber thickness (0.5–5 µm), contact work function (4.3–5.65 eV), doping and defect densities, bias voltage (−5 V to +5 V), temperature and interlayer thickness are systematically varied. Shadowing, carrier transit time and the RC limit specific to the interdigitated electrode structure are incorporated through analytical corrections. Dark current, photo-to-dark current ratio, quantum efficiency, responsivity, specific detectivity, noise equivalent power and 3 dB bandwidth are extracted, and the speed-efficiency trade-off is evaluated using the bandwidth-efficiency product. By comparing Si, GaAs, GaN and heterostructure options, the study aims to identify optimal design ranges for high-speed, high-responsivity and low-noise scenarios. The work is expected to provide a quantitative design guideline for experimental MSM photodetector studies without resorting to costly fabrication processes.