Anodic oxides on InAlP formed in sodium tungstate electrolyte

Amorphous anodic oxide films on InAlP have been grown at high efficiency in sodium tungstate electrolyte. The films are shown to comprise an outer layer containing indium species, an intermediate layer containing indium and aluminium species and an inner layer containing indium, aluminium and phosphorus species. The layering correlates with the influence on cation migration rates of the energies of In3+–O, Al3+–O and P5+–O bonds, which increase in this order. The film surface becomes increasingly rough with increase of the anodizing voltage as pores develop in the film, which appear to be associated with generation of oxygen gas.