Ultrafast Room‐Temperature Nanofabrication via Ozone‐Based Gas‐Phase Metal‐Assisted Chemical Etching for High‐Performance Silicon Photodetectors

Abstract High‐aspect‐ratio silicon nanostructures are essential building blocks for next‐generation electronics, but their fabrication remains challenging due to process complexities and structural instabilities. Here, this study presents an unprecedented gas‐phase metal‐assisted chemical etching (GP‐MACE) strategy using high‐purity ozone (O 3 ) as an oxidizing agent. This approach achieves remarkable etching rates of ≈1 µm min −1 at room temperature—70 times faster than conventional oxygen‐based processes—while maintaining superior structural integrity. The enhanced oxidation potential of O 3 (E 0 = 2.08 V) enables precise control over the etching mechanism, yielding vertical nanowires with minimal surface defects, as confirmed by the unity critical‐depth‐to‐maximum‐depth ratio and three‐fold reduction in surface porosity compared to liquid‐phase processes. Leveraging this exceptional structural quality, it demonstrates high‐performance photodetectors utilizing a doping‐free Al 2 O 3 /Si core‐shell architecture. The conformal Al 2 O 3 coating induces an inversion layer that functions analogously to a p‐n junction while simultaneously providing surface passivation, enabling efficient carrier separation without conventional thermal doping. The photodetector exhibits superior responsivity (0.45 A W −1 ) and stable switching characteristics even under zero‐bias conditions. This room‐temperature nanofabrication strategy, combining unprecedented etching rates with superior structural control, provides a promising platform for industrial‐scale manufacturing of high‐performance nanodevices.