Reactivity of heteropolyanions toward GaAs compound

We studied the reactivity of GaAs in;contact with acidic solutions of, resp ectively, four heteropolyanions (HPAs): SiW12O404-, SiMo12O404-, PW12O403-, and P2W18O626-; The results obtained by both x-ray photoelectron spectrosc opy and etching rate and absorbance measurements showed that GaAs dipped in to such solutions undergoes an oxidation/dissolution process while the HPAs are reduced. Indeed, after each immersion of GaAs into an heteropolyanioni c solution, a deposit, which consists of As-0 atoms with either partially r educed HPA or WO3 is observed. This study has given us the opportunity to d etermine the reactions which occur at the GaAs/''HPA solution'' interface a nd to point out the importance of the semiconductor energy-band position wi th respect to the first redox potential of the HPA. Knowledge of the semico nductor/HPA energetic dia,sram allows one to predict the behavior of HPA sp ecies toward semiconductors. (C) 2000 American Vacuum Society. [S0734-2101( 00)07805-2].