Investigation of Quantum Confinement Effects in Silicon Nanowire Field-Effect Transistors Fabricated by Metal-Assisted Chemical Etching

Background: Silicon nanowire field-effect transistors exploit quantum confinement to achieve superior electrostatic control and reduced short-channel effects compared with bulk silicon devices. Metal-assisted chemical etching offers a low-cost, scalable fabrication route accessible to Nigerian research facilities. Aim: This study investigated quantum confinement effects in silicon nanowire FETs fabricated by metal-assisted chemical etching and characterised their structural, electronic, and transport properties. Methods: Silicon nanowires with diameters from 5 to 50 nm were fabricated by silver-assisted chemical etching of p-type silicon wafers. Structural characterisation was performed by transmission electron microscopy and Raman spectroscopy. FETs were fabricated using photolithography and characterised by current-voltage and capacitance-voltage measurements. Effective mass and band structure modifications due to quantum confinement were extracted by comparison with k.p perturbation theory calculations. Results: Clear quantum confinement effects including blue-shifted photoluminescence and increased carrier effective mass were observed for nanowires below 10 nm diameter. Nanowire FETs with 8 nm diameter channels showed subthreshold slope of 68 mV/decade and on-off ratio exceeding 107. Carrier mobility decreased from bulk values due to surface roughness scattering. Conclusion: Metal-assisted chemical etching produces functional silicon nanowire FETs exhibiting clear quantum confinement effects. Surface passivation strategies to reduce scattering are identified as the key challenge for device optimisation. Keywords: silicon nanowire, quantum confinement, field-effect transistor, metal-assisted etching, carrier transport.