Growth of Anodic Oxides on n-InP Studied by Electrochemical Methods and Surface Analyses

Abstract

Growth, formation, and stability of anodic oxides obtained on n-InP were investigated by coupling electrochemical methods and X-ray photoelectron spectroscopy ͑XPS͒ analyses. Photocurrent transients and capacitance measurements performed before and after the semiconductor surface oxidation exhibit new electrical interfacial properties, whereas XPS analysis gives access to chemical composition and estimation of oxide layer thickness. In this work, using a galvanostatic method, oxidation of the InP surface has been studied at pH 9 for two current densities: 0.2 and 12 mA cm −2 . Using transient photocurrent and Mott-Schottky behavior as in situ probes, we have pointed out several steps for the InP oxidation process, correlated to a gradual oxide coverage which is evidenced by XPS characterization. The current density chosen to perform the oxidation governs the resulting chemical composition, texture, and electrical properties of the oxide. For low current density, the anodic mechanism varies progressively from a pure semiconductor oxidation process to a solvent oxidation contribution. For high current density, this trend disappears whereas semiconductor oxidation continues to take place.

Photopotential Measurements on Undopedn-InP at Open Circuit Potential According to the Aqueous pH

“…Such positive shifts of C −2 = f(E) plots have already been observed at pH 9, on doped (10 18 atoms.cm −3 ) n-InP semiconductor after an external positive polarization under illumination. 24,25,20 In these previous works, the illumination under positive polarization generated an anodic photocurrent transient which was associated to the anodic oxidation of InP surface and the growth of a thin "InPO 4 -like" oxide layer. 24,25 The positive shift of the Mott-Schottky plot was clearly attributed to a chemical modification of the SC surface.…”

“…20 InP electrodes were successively immersed in several buffered aqueous solution. A local variation of the pH induces an evolution of the potential drop through the Helmholtz layer which was considered as capacitive component (C H ).…”

“…The modifications of peak energy distribution with an oxide layer and their attribution in terms of oxide compositions have been well discussed and documented in the literature. 20,24,[26][27][28][29][30][31] Furthermore, referring to the literature and to the experimental data showing a positive shift of the flatband potential by capacitance measurements and new contributions of P 2p and In 3d peaks positively shifted by XPS analyses, the interface was classically characterized by the formation of a thin oxide with a composition close to InPO 4 . For undoped n-InP, under positive external polarization and under illumination, the formation of InPO 4 -like compound could be also suggested from capacitance measurements and XPS analyses (Fig.…”

Förster resonance energy transfer between individual semiconductor nanocrystals and an InP film

“…[30][31][32][33] In the present paper, the anodic treatment of the InP surfaces has been performed in a borate buffered solution at pH 9 leading to the growth of an "InPO 4 -like" layer with good chemical and electrical properties. 29,34,35 By varying the time and/or the current density, the thickness of the resulting oxide layer can be controlled, which is of importance in our study since it determines the distance between the absorber material and the semiconductor surface. The InP bare surfaces are purchased from the company Sumitomo Electric and are n-doped, with a dopant concentration of 10 18 ∕cm 3 .…”

Fundamental Study of InP-Based Open-Gate Field-Effect Transistors for Application to Liquid-Phase Chemical Sensors

“…In such a situation, the surface potential can only be slightly changed with the ion concentration in the electrolyte. Various approaches for reducing the interface states have been proposed for the InP, such as sulfur treatments [14][15][16] , application of a Si interface layer 17) , and electrochemical treatment 18,19) . For example, a large reduction in the interface states was achieved for the SiN x /InP interfaces by using a gaseous H 2 S treatment, which resulted in recovery of the potential controllability 15) .…”