XPS investigation of anodic oxides grown on p‐type InP

Chemical composition of anodic oxides grown on lightly doped p‐type InP have been investigated by XPS. Anodization was performed in the constant current density ( J c ) mode using an ortho‐phosphoric acid solution mixed with acetonitrile (ACN). The electrolyte was chosen after experimentation on the effect of the anodization parameters (electrolyte, viscosity of the electrolyte and pH, J c and illumination level) and annealing conditions on the uniformity and stability of the oxide and the contamination level, as determined by SEM/EDAX, SIMS and XPS. Based on our XPS investigation, it appears that the inhomogeneity with depth of the anodic oxides grown on p‐type InP is strongly dependent on the growth conditions. Depending on the anodization procedure, the anodic oxide appears complex and the presence of In(OH) 3 , In 2 O 3 , InPO 4 , In(PO 3 ) 3 , In(PO 3 ) 4 and other non‐stoichiometric In(PO y ) x compounds have been identified. Depending on the anodization conditions, it appears that both amorphous and crystalline phosphorus‐rich condensed phosphates, of interest for surface passivation of InP, can be grown on p‐type InP.