Optical sensing performance and electrostatic reliability of silicon nanowire reconfigurable phototransistors

This work presents, for the first time, a rigorous investigation of the optical sensing performance and design of silicon nanowire (Si-NW) reconfigurable phototransistors (RPTs) over a broadband wavelength range spanning the ultraviolet (UV), visible, and near-infrared (NIR) regions. To study the design of these RPT devices, a well-calibrated simulation framework is developed under both dark and illuminated conditions to evaluate and compare the electronic, transfer, transient, and optical characteristics for p-type and n-type operations. The baseline device exhibits a peak responsivity of 180 mA/W and a photosensitivity of 5 × 104 within the UV and visible spectral ranges. The impact of temperature on optical sensing performance was also investigated, demonstrating excellent thermal stability and reliable sensing capability under harsh environmental conditions. The reliability of optical sensing performance and electrostatic behavior is further evaluated by adjusting the gate overlap positions of the control and program gates on the nanowire channel, while keeping the original physical process parameters. The influence of control and program gate positions is analyzed through energy band diagrams, carrier density profiles, responsivity, and dark current characteristics. Optimal gate placements are identified to enhance photo-absorption without adversely affecting the dark-state transfer characteristics or the physical baseline device dimensions. With optimized control and program gate positions, a peak responsivity of 315 mA/W is achieved, representing an enhancement of ∼1.8× while maintaining reliable electrostatic behavior of the RPT devices. This single device demonstrates reliable operation in both polarities (n-type and p-type), enabling simplified integration into silicon photonic platforms and reducing the need for separate complementary detector structures. Thus, this study establishes a promising foundation for integrating Si-NW RPT into advanced CMOS-compatible on-chip photonic platforms targeting UV, visible, and NIR wavelength detection.