The effect of oxidizing agent HCHO on the electrochemistry and etching morphology of p-type and n-type (100) silicon electrodes in a KOH solution has been studied.The results indicate that HCHO has a strong influence on the anodic behavior of both p-Si and n-Si electrodes in alkaline solutions.A reduction current of HCHO on an n-Si(100) electrode was observed in the dark due to the conduction band electron.The electrochemical reduction of HCHO on a p-Si(100) could only be observed under illumination.In this case a photocurrent doubling phenomenon was observed.It was suggested that reduction of HCHO in alkaline solution occurs in two steps, giving methanol as the final reaction product.It was found that HCHO could be used to control the surface morphology of silicon during chemical etching in alkaline solutions.

Key words: silicon, oxidizing agent, formaldehyde, chemical etching, pyramid suppression