Oxidation Of InP Research Articles

First principles study on InP (001)-(2 × 4) surface oxidation

A theoretical study of the oxidation of InP(001)-(2 × 4) surface is performed using density functional theory methods. Our results on surface oxidation show that the oxygen adsorption does not produce any gap states in the bulk InP band gap, due to the saturation of surface In dangling bonds, whereas substitutional oxygen atoms produce gap states. This study also shows that the surface stability increases with the oxygen content, indicating a strong tendency for surface oxidation. Our results help to clarify the origin of surface gap states upon surface oxidation and provide an insight at the atomic level the mechanism of surface oxidation, which will assist in the understanding of the degradation of III-V devices upon oxygen exposure or interfacial oxidation with high dielectric constant oxides.

High-speed determination of the thickness and spectral ellipsometry investigation of films produced by the thermal oxidation of InP and V x O y /InP structures

Spectral ellipsometry was used to determine the thickness and optical properties of films produced by the thermal oxidation of InP and VxOy/InP structures. Comparison of the measured optical characteristics and thickness of nanofilms with high-speed ellipsometric analysis data indicates that the two methods should be used in the case of multicomponent films. Absorption in such films is shown to be due, among other factors, to the presence of unoxidized indium, which influences the optical properties of the film and the ellipsometric measurement results.

Impact of substrate temperature and film thickness on the interfacial evolution during atomic layer deposition of HfO2 on InP

AbstractThe effects of both the deposition temperature and the HfO2 film thickness on the interfacial layer (IL) evolution were studied when tetrakis(ethylmethylamino)hafnium and H2O based atomic layer deposition (ALD) was performed on InP substrates. While the self‐cleaning effect resulted in an IL‐free structure after formation of ∼2 nm thick HfO2 at 200 °C and 250 °C, substantial IL growth occurred at 300 °C, probably due to simultaneous InP oxidation. Following further growth to ∼8 nm at 300 °C, the IL was almost removed and, in particular, a significant In incorporation into the HfO2 film was observed, which was attributed to IL decomposition and subsequent out‐diffusion of the constituent elements. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Stability of InP oxide versus solvated electrons in liquid ammonia

Abstract In alkaline aqueous medium (pH 9), potassium ferricyanide was used as an oxidizing agent on InP. This electroless process was successfully controlled by capacity measurements, AFM and XPS analyses. For the first time, the chemical stability of the oxide has been studied against the strongest reducing agent in liquid ammonia (−50 °C): the solvated electron. It was obtained in two ways; an electroless process which involved the addition of metallic potassium and by cathodic galvanostatic treatment on InP in neutral medium. As a first result, the electroless process required a strong rinsing step of the surface by pure liquid ammonia. As a second result, the galvanostatic process gave also promising results. A significant decrease of the amount of oxide was evidenced by capacity measurements, AFM and XPS analyses.

Growth of vanadium oxide films on InP under mild conditions and thermal oxidation of the resultant structures

Techniques have been developed for producing vanadium oxide films (10 nm to 1 μm thick) on indium phosphide using vanadium(V) oxide gels and sols through immersion and deposition from aerosol. Using scanning tunneling microscopy and X-ray diffraction, we have studied the influence of annealing temperature and time on the morphology and composition of the films and the influence of the films on the thermal oxidation of InP.

Effect of V2O5 nanoislands on the surface composition and structure of InP during thermal oxidation

The evolution of the surface morphology and composition during the thermal oxidation of InP in the presence of V2O5 nanoislands has been studied by scanning tunneling microscopy and Auger electron spectroscopy. The results demonstrate that the effect of the islands is strongest in the initial stage of the process and persists in later stages. Auger electron spectroscopy and kinetic data strongly suggest that the oxidation of InP in the presence of vanadium oxide nanoislands follows a catalytic mechanism.

Thermal oxidation of AIIIBV semiconductors with V2O5 nanolayers on the surface

The specific features of the interaction of vanadium(V) oxide nanofilms with the surface of gallium arsenide and indium phosphide semiconductors under thermal oxidation conditions have been considered. The kinetics and mechanism of thermal oxidation of GaAs and InP with deposited V2O5 layers 15 and 25 nm in thickness have been studied. It has been revealed that vanadium(V) oxide exerts a specific effect on the oxidation of gallium arsenide and indium phosphide as compared to other d-metal oxides. It has been established that the oxidation occurs with the formation of a phase predominantly consisting of indium phosphates or gallium arsenates and intermediate products based on vanadium compounds in different oxidation states. Schemes have been proposed for the development of the oxidation processes with due regard for the chemical nature of vanadium(V) oxide.

Thermal oxidation of InP with V2O5 + PbO nanolayers of different compositions

Data are presented on the thermal oxidation of (V2O5 + PbO)/InP structures which demonstrate that the combined effect of the oxides deposited by magnetron sputtering does not follow the additivity rule and that this behavior is due to the formation of a quasi-liquid phase (maximum) and lead vanadate (minimum) (IR spectroscopy, Auger electron spectroscopy). The effective activation energy for the oxidation of the (V2O5 + PbO)/InP structures is shown to systematically decrease with increasing initial vanadium oxide content. The oxidation of the structures follows a partially catalytic mechanism, with V2O5 acting as a catalyst (oxidation kinetics, IR spectroscopy, ultrasoft X-ray emission spectroscopy).

Electron band alignment between (100)InP and atomic-layer deposited Al2O3

Energy barriers at interfaces of (100)InP with atomic-layer deposited Al2O3 are determined using internal photoemission of electrons. The barrier height between the top of the InP valence band and bottom of the alumina conduction band is found to be 4.05±0.10 eV corresponding to a conduction band offset of 2.7 eV. An interlayer associated with the oxidation of InP may result in a lower barrier for electron injection potentially leading to charge instability of the insulating stack. A wide-gap P-rich interlayer has a potential to reduce this degrading effect as compared to In-rich oxides.

The dependence of the oxidation enhancement of InP(100) surface on the coverage of the adsorbed Cs

We report the oxidation of the InP(100) surface promoted by adsorbed Cs by synchrotron radiation photoemission. Oxygen exposure causes reduction in the charge transferred to the InP substrate from Cs and the growth of indium oxide and phosphorous oxide. The oxide growth displays a clear dependence on the Cs coverage. The oxidation of phosphorous is negligible up to 1000 L of O2 exposure when the Cs coverage is less than half a monolayer (ML) but the formation of the second half-ML of Cs greatly accelerates the oxidation. This different enhancement of the InP oxidation by the first and the second half-ML of Cs is due to the double layer structure of the adsorbed Cs atoms, and consequently the higher 6s electron density in the Cs atoms when Cs coverage is larger than 0.5 ML.

X-ray diffraction analysis of multilayer porous InP(001) structure

Multilayer structures composed of four porous bilayers have been studied by high-resolution X-ray diffraction using synchrotron radiation, and the photoluminescence of these structures has been investigated at 4 K. The porous structures were formed by anodic oxidation of InP(001) substrates in aqueous HCl solution. The structural parameters of the sublayers were varied by changing the electrochemical etching mode (potentiostatic/galvanostatic). The X-ray scattering intensity maps near the InP 004 reflection are obtained. A model for scattering from such systems is proposed based on the statistical dynamical diffraction theory. Theoretical scattering maps have been fitted to the experimental ones. It is shown that a mathematical analysis of the scattering intensity maps makes it possible to determine the structural parameters of sublayers. The reconstructed parameters (thickness, strain, and porosity of sublayers and the shape and arrangement of pores) are in satisfactory agreement with the scanning electron microscopy data.

Spontaneous Deposition of Metallic Pt onto n-InP: An Electroless Process

InP surface are treated in K2PtCl4 dissolved in pure water. A spontaneous electroless process is observed with interesting residual Pt(0) coverage an correlated InP oxidation. The demonstration of this effect is given by high resolution XPS. Modifications are also detected using capacitance measurement on the interface.

A Significant Anodic Passivation of n and p-InP Surfaces in Liquid Ammonia: First Evidence of Stable Phosphorus-Nitrogen Bonds

The anodic electrochemical treatment in liquid ammonia of InP (n- and p-) leads to a simultaneous oxidation of both semiconductor and solvent. The oxidation of InP takes place through a passivating layer revealed as well by electrochemistry as by XPS. The chemical composition of InP surface is therefore gradually modified according the anodic charge. The composition of the film layer is supposed to be close to HN=P-NH2, a promising compound stable as well in liquid ammonia as in water.

The Role of the Surface Chemistry on the Evolution of Kinetic of Hole Injection by Fe(CN)6 3- at n- InP

Study of InP in Fe(CN)63- solution at pH9 are presented. Modifications of cyclic voltammograms are observed and correlated to presence of thin InP oxide that change the capability of the electronic transfer through the interface.

Growth and Formation of Thin Anodic Films on InP

Growth, formation and stability of anodic oxides obtained on n- InP were investigated by coupling electrochemical methods and XPS analyses. Using transient photocurrent and Mott-Schottky behavior, as in situ probes, we have pointed out several steps for InP oxidation process, related to a gradual oxide coverage evidenced by XPS characterizations. The current density chosen to perform the oxidation governs the resulting chemical composition, the texture and the electrical properties of the oxide. Low applied current densities lead to the formation of thin (around few nanometers) and homogeneous films, while high current densities induce thicker and less homogeneous oxides. The resulting electrical properties also strongly depend on the anodization mode. The thinner homogeneous layers, grown with low current densities, exhibit the best passivating features.

Effect of PbO layers with nickel oxide and vanadium oxide additions on the thermal oxidation of InP

IR and ultrasoft x-ray emission spectroscopy data indicate that the thermal oxidation of PbO/InP structures with additions of transition-metal (nickel and vanadium) oxides leads to the formation of multicomponent layers consisting of nickel, vanadium, lead, and indium phosphates. These oxide additions to PbO nanolayers accelerate the thermal oxidation of InP. A small amount of vanadium oxide added to PbO gives rise to a significant contribution of a catalytic mechanism to the accelerated thermal oxidation of InP. The principal distinction between the PbO/InP and (PbO + NiO)/InP structures is that the thermal oxidation of the latter leads to the formation of an InxNiyPz transition layer, which influences the growth rate and the composition of the resulting layer.

Self-organized nanodot formation on InP(1 0 0) by oxygen ion sputtering

We demonstrate the formation of ordered nanodot chains with dot size less than 100 nm by 1 keV O 2 + beam sputtering on InP(1 0 0). The ordered nanodot chains are perpendicularly aligned to the ion beam direction, and are formed at 38° and 44° incidence with ion current density of 100 μA cm −2. At 56° and 62° incidence, the nanodot chains formed are shorter and more coarse, and the periodicity of the nanodot chains is suppressed. XPS analysis show that the surface of nanodots formed comprise In 2O 3 and various InP oxides; and is In 2O 3-rich due to the preferential sputtering of P atoms.

The role of nitrogen-containing compounds in the growth of oxide layers on GaAs and InP in the course of their thermal oxidation

Thermal oxidation of GaAs and InP with the participation of nitrogen-containing compounds (such as NH3, N2O, NH4NO3, NH4VO3, and NH3 + V2O5) is investigated. It is found that the rates of growth of oxide layers on the surface of semiconductors increase significantly when the chemical activator undergoes transformations in the reaction zone with the formation of compounds that are active at the instant of formation.

Combined effect of V2O5 and NH3 on thermal oxidation of InP

The combined effect of V2O5 and NH3 on thermal oxidation of InP in a wet oxygen atmosphere is investigated experimentally.

Wet chemical cleaning of InP surfaces investigated by in situ and ex situ infrared spectroscopy

Wet chemical cleaning is central to semiconductor device processing. For InP-based optoelectronic devices, controlling wet processing is challenging because of the high reactivity of InP surfaces in ambient air. In situ techniques are therefore critical to monitor and understand wet chemical etching and oxidation. We have combined in situ and ex situ Fourier transform infrared absorption spectroscopy, in direct transmission and multiple internal reflection configurations, with ex situ x-ray photoelectron spectroscopy to investigate the wet-chemical removal of “epi-ready” oxides on InP(100). Even dilute solutions of HCl, HF, or H2SO4 are found to completely remove the epi-ready oxides. For both HCl and HF, the InP surface is left unpassivated, exhibiting rapid recontamination and reoxidation upon air exposure. In contrast, H2SO4 aggressively etches the surface, and forms a thick and fragile oxide cap that can be washed away during a subsequent water rinse. This systematic in situ vibrational study of InP oxide chemistry provides a basis for a mechanistic understanding of wet chemical etching and oxidation.