Anomalous photoelectrochemical etching of undoped semiconductor surfaces.

For more than 60 years, it has been widely accepted that the irradiance of the incoming light plays the most critical role in the etching effect of the photoelectrochemical etching process, which is built upon the underlying physics that photo-generated charge carriers catalyze the dissolution of n-type semiconductors. However, in this paper, we report an anomalous physical phenomenon, i.e., the spatially distributed photons with a lateral gradient could drive the lateral distribution of carriers on the surface of semiconductors, which leads to the anomalous etching phenomenon on the surface of undoped semiconductor materials during the PEC etching process. Research shows that parameters such as light intensity, light intensity gradient, and carrier diffusion length are significantly correlated with this process. This discovery provides a potential method of rapid and large-scale 3D nanomanufacturing on semiconductor materials, which holds promise for significant applications in diverse fields such as microelectronics, nanophotonics, microelectromechanical systems (MEMS), and biomedicine.