Effects of temperature and current density on the porous structure of InP

The electrochemical oscillations that occur during the etching of InP and the three-dimensional (3D) porous structure of the resulting material were studied by performing electrochemical etching in a 3.5 mol L−1 NaCl solution at different temperatures and current densities. The characteristics of the oscillations were modified by adjusting the electrochemical parameters. The relationship between the oscillations and the porous structure of the etched InP was investigated. In the experiments, porous InP with a gradient-index (GI) structure was formed at relatively low temperatures (10–22 °C) and current densities (100–300 mA cm−2). Furthermore, two types of incomplete pores observed in the bottom layer of the porous structure of InP were found to correspond to incomplete oscillations (one-quarter and one-half of an oscillation, respectively), which provided useful insight into how pore growth proceeds in the etched InP. Based on the results obtained in this work, the growth mechanism of porous InP is discussed in this article.