A Processing Window for Fabricating Heavily Doped Silicon Nanowires by Metal-Assisted Chemical Etching

Abstract

Heavily doped silicon nanowires (SiNWs) with controllable doping concentrations can be used in many fields because of their unique characteristics. However, it is difficult to fabricate long heavily doped SiNWs. In this article, a systematic study of metal-assisted chemical etching (MACE) of heavily doped silicon wafers is presented. High-quality SiNWs with lengths up to 40 μm could be achieved. The electron-transfer processes among Si, Ag +, Ag nanoparticles, and H 2 O 2 were investigated to explain the formation of SiNWs. A chemical etching processing window, considering HF and H 2 O 2 concentrations, reaction temperature, and etching time, is proposed. To obtain SiNWs, the etching reaction should occur at room temperature for less than 40 min. The appropriate concentration ranges are 0.2–0.4 M for H 2 O 2 and 8–10 M for HF. Transmission electron microscopy (TEM) measurements confirmed that the as-prepared nanowires were single-crystalline. Current–voltage ( I – V ) measurements of an individual nanowire showed a resistance larger than the calculated value based on bulk silicon. This work can provide guidelines for obtaining high-quality heavily doped SiNWs using the MACE method.