Study on the Etching Characteristics and Thermal Conductivity of Porous Silicon Nanowire Arrays Using Highly Doped Silicon

Abstract

Silicon nanowires (SiNWs) fabricated by metal-assisted chemical etching (MACE) of highly doped silicon are promising thermoelectric materials because of their high conductivity and porosity. However, it is difficult to fabricate long SiNWs using highly doped silicon with doping concentrations higher than 10¹⁹ cm⁻³. In this study, we fabricated SiNWs up to 44 μm in length using highly doped silicon with a doping concentration of 10²⁰ cm⁻³, analyzed the etching characteristics in SiNWs length and the morphology, and investigated the thermal conductivity. The phenomenon of continuous loss of SiNWs was found, which is a unique phenomenon indicating the presence of loss SiNWs throughout the whole etching process and difficulty of forming long SiNWs with highly doped silicon. On the other hand, the thermal conductivity results showed that the lowest thermal conductivity of the samples reached 2.98 W m⁻¹ K⁻¹, and the mean diameters of pores in these samples were 5−10 nm. Thus, the SiNWs using highly doped silicon is a potential material for thermoelectric device.