Photoanodic oxidation of InP in acid solution and its surface chemistry: On the interplay of photons, protons and hydrodynamics

• DOI: 10.1016/j.electacta.2020.136872
• Publication Date: 2020-08-05T00:29:13Z
• Authors: Dennis H. van Dorp; Genis Vanheusden; Kris Paulussen; Ibrahim Hassan; Simon Van Wonterghem; Graniel H. Abrenica; Praveen Dara; Johan Meersschaut; Thierry Conard; Frank Holsteyns; John J. Kelly
• Keywords: Passivation; Anodic oxidation; Native oxide; Taverne; GaAs; InP; Surface chemistry; 01 natural sciences; 7. Clean energy; 0104 chemical sciences

Factors determining etching and passivation of n-type InP in H2SO4 and HCl solution and the corresponding surface chemistry are considered. Passivation is favoured by higher light intensity and lower proton and Cl− ion concentration. Ex-situ surface analysis shows the passive (bi)layer to consist mainly of oxide-based In3+ and P5+ components: InPO4 and In(PO3)3. Hydrodynamics is found to play a decisive and surprizing role in determining the kinetics of the surface reactions. Oxygen-bridge formation between surface In and P atoms, as a result of deprotonation of a P-OH reaction intermediate, is considered to be important in determining competition between the two reaction paths: etching and passivation. These results are compared with markedly contrasting results for n-type GaAs under similar experimental conditions.