In the presence of alpha-SiMo12O404- ions dissolved in acidic solution and under laser irradiation, the electroless photoetching of n-type InP is achieved. At the laser impact, the semiconductor is oxidized while SiMo12O404- species are reduced. The shape of the pit formed, due to the photoanodic dissolution of the material, depends on the experimental conditions, notably on the presence or not of Cl- ions in the medium. It can have either a Gaussian shape or a flat bottom. To specify the charge transfer which occurs at the n-InP/solution illuminated interface, some electrochemical studies were performed on n- and p-type InP electrodes. In fact, the reduction of SiMo12O404-ions occurs by capture of electrons from the InP conduction band. Considering the energetic situation at the InP/electrolyte interface and some electrochemical results, it is concluded that the electron transfer from InP to SiMo12 is mediated by surface states. The influence of Cl- ions on the n-InP photodissolution process is also discussed. (C) 2004 Elsevier Ltd. All rights reserved.