Engineered etching and laser treatment of porous silicon for enhanced sensitivity and speed of Pt/n-PSi/Pt UV photodetectors.

Abstract

Silicon-based photodetectors offer notable advantages in cost, performance, and reliability. However, while nanoscale silicon (porous silicon, PSi) effectively emits visible light, it remains inefficient as an indirect-bandgap semiconductor. To improve its optoelectronic properties, coupling silicon with a wide-bandgap semiconductor is a promising strategy. In this study, nanoporous silicon (n-PSi) films were fabricated from an n-type Si (111) wafer using optimized photoelectrochemical etching (PECE). These films were then irradiated with Q-switched Nd:YAG laser pulses (3, 5, 10, and 20 pulses) at a fixed wavelength of 1068 nm, with pulse durations ranging from 3 to 20 ns and a constant repetition rate of 10 Hz. The structural, morphological, and optical properties of both as-prepared and laser-annealed n-PSi samples were characterized using various analytical techniques. Among the laser-treated samples, n-PSi subjected to three laser pulses exhibited the highest crystallinity and largest crystallite size (∼87.02 nm). This optimized sample was selected for fabricating a Pt/n-PSi/Pt metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector. The photoluminescence spectra of the fabricated devices revealed strong near-band-edge (NBE) emission, with a violet band centered around 523 nm, corresponding to a bandgap energy of 2.36 eV. The I-V characteristics of the MSM UV photodetectors were analyzed under dark conditions and 380 nm UV illumination. The device demonstrated high photosensitivity (951.28), excellent responsivity (2.01 A W^-1), and fast response (0.44 s) and recovery (0.48 s) times, outperforming conventional photodetectors. This approach provides a viable pathway for tuning nanomaterials with tailored properties for high-performance nanodevices. The fabricated MSM UV photodetectors show great potential for next-generation optoelectronic applications.