The chemical state of sulfur on (NH4)2Sx‐treated InP(001) surfaces has been studied by high‐resolution x‐ray photoelectron spectroscopy. We find three kinds of chemical states of sulfur (S2p3/2 lines at 161.2, 162.0, and 163.4 eV) on the sample treated at RT. It is suggested that they correspond to sulfur in phosphorus sites (in the second layer of the InP(001) surface), to sulfur bonded to indium on the first layer, and to elemental sulfur on sulfide, respectively. One (S2p3/2=162.0 eV) of them becomes predominant with long‐time exposure to atmosphere at RT. Upon annealing the sample at 400 °C, the 163.4 eV line disappears, while the lines at 162.0 and 161.2 eV remain on the surface. A model of the treated surface is presented.

(NH4)2Sx‐treated InP(001) studied by high‐resolution x‐ray photoelectron spectroscopy

Fabrication of high‐quality InP metal‐insulator‐semiconductor field‐effect‐transistor (MISFET) devices implies that adequate passivation of the surface can be achieved. In this paper, a passivation process of the InP surface, is presented using In(PO3)3‐like condensed phosphates. An extensive study of the physicochemical and structural properties of these oxides and of the microscopic properties of its interface with InP is carried on, using a combination of various techniques (reflection high‐energy electron diffraction, x‐ray photoelectron spectroscopy, ellipsometry, and high‐resolution transmission electron microscopy). High‐quality MISFET devices have been fabricated; the high performances obtained in terms of transconductance and stability are well correlated with the good intrinsic properties of the oxides.

Passivation of InP using In(PO3)3‐condensed phosphates: From oxide growth properties to metal‐insulator‐semiconductor field‐effect‐transistor devices

Reconstruction of an InP(001) surface structure upon H2S adsorption has been studied by low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), high-resolution electron energy loss (HREELS), and x-ray photoelectron spectroscopies (XPS). The HREELS result indicates that H2S is dissociated on the surface even at RT, leading to evolution of hydrogen from the surface. LEED patterns show (2×4) and (2×1) structures for the surface with sulfur coverages, 0 and 0.5–1 ML, respectively. A complex pattern appears at 0.25 ML. We find in STM images that the (2×1) structure starts to form even at 0.1 ML sulfur coverage at 350 °C. The (2×1) structure is almost established at 0.5 ML although the protrusions of about two atoms in size exist on the surface. The new (2×1) structure begins to grow from protrusions above 0.5 ML on the (2×1) surface found at 0.5 ML and it is established at about 1 ML where the c(2×2) structure with small domain is found. XPS result shows one chemical state of sulfur at 0.5...

Surface reconstruction of InP(001) upon adsorption of H2S studied by low-energy electron diffraction, scanning tunneling microscopy, high-resolution electron energy loss, and x-ray photoelectron spectroscopies

We find two different surface structures, (1×2) and (1×1), for H2S‐treated InP(001). They depend upon exposure of H2S at about 350 °C. The coverage of sulfur is estimated to be about a half monolayer and one full monolayer for the (1×2) and (1×1) structures, respectively. The (1×1) structure is reconstructed to the (1×2) structure upon annealing at about 550 °C. It is suggested that sulfur is bonded to only In atoms and substitutes some of the phosphorus atoms below the first layer. Inverse photoemission spectra show strong reduction in intensity of 1.2 eV peak above the Fermi level for a clean InP(001)‐(4×2) surface upon adsorption of H2S. This reduction implies a decrease in unoccupied surface states due to dangling bonds of indium dimers on the clean surface. The result of adsorption of oxygen on the (1×2) and (1×1) surfaces indicates significant passivation to oxidation of the surfaces.

Surface structures and electronic states of H2S‐treated InP(001)

Spatially distributed states within the insulator are thought to be the origin of the well‐known drift phenomena usually found in InP metal–insulator semiconductor (MIS) devices. This paper will show that the concentration of these states can be reduced drastically by applying a suitable deposition technique. Plasma‐enhanced chemical vapor deposited SiO2 is used as the insulator in a process involving low substrate temperatures (200 °C), spatial separation of sample and plasma (indirect plasma method), and the addition of phosphorus into the reaction chamber during the initial stage of insulator deposition. The influence of several process parameters on the properties of the silicon dioxide films as well as the SiO2/InP interface characteristics are investigated. Deep level transient spectroscopy and C(V) measurements of InP MIS capacitors yield concentrations of slow insulator states of only 1–2×1011 cm−1 eV−1 for the best of our samples.

Reduction of the concentration of slow insulator states in SiO2/InP metal-insulator semiconductor structures

A new approach is presented for the development of a metal‐insulator–semiconductor field‐effect transistor technology. It is applied to the optimization of Al2O3/InP structures prepared by the deposition of evaporated Al2O3 on arsenic‐stabilized InP surfaces. Molecular beam epitaxy and surface‐science techniques (reflected high‐energy electron diffraction and x‐ray photoelectron spectroscopy are used to control step by step the fabrication of the structures and to describe the microscopic properties of the interfaces. The optimization of the fabrication process is based on correlations between interfacial physicochemical properties and metal–insulator‐semiconductor capacitor electrical properties. It is shown that an interfacial oxide buffer layer can favor crystallochemical matching between Al2O3 and InP.

The passivation of InP by arsenic surface stabilization and Al2O3 deposition: Correlations between interface chemistry and capacitance measurements

Nous avons utilise la diffraction d'electrons RHEED et la spectroscopie XPS pour etudier les proprietes structurales et chimiques de la surface d'InP au cours des differentes phases de la formation de l'interface du systeme Al2O3/As$/\!\!/$InP elabore par le depot d'Al2O3 sur une surface d'InP prealablement traitee thermiquement sous un flux d'arsenic et oxydee. Ces proprietes sont correlees aux proprietes electriques de l'interface estimees sur la base de mesures capacitives. Nous mettons ainsi en evidence d'une part, que les meilleures proprietes electriques sont obtenues lorsque l'ordre structural de la surface d'InP est restaure et, d'autre part, le role determinant joue par la chimie de l'interface. En particulier, nous montrons qu'un oxyde d'arsenic a l'etat d'oxydation As+5 peut favoriser l'accord cristallochimique entre l'Al2O3 et la surface d'InP$/\!\!/$As et ainsi ameliorer les proprietes electriques de l'interface.

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Rôle de la zone interfaciale dans la qualité des proprietés électriques du système Al2O3/As$/\!\!/$InP

A new approach is presented for the development of a MISFET technology. It is applied to the optimization of A1203/InP structures prepared by the deposition of evaporated A1203 on arsenic stabilized InP surfaces. MBE and surface science techniques (XPS and RHEED) are used to control step by step the elaboration of the structures and to describe the microscopic properties of the interfaces. The optimization of the elaboration process is based on correlations between physico-chemical properties and MIS electrical properties. It is shown that an interfacial oxide buffer layer can favor chemical matching between A1203 and InP.

R. Skheyta

Papers

The passivation of InP by arsenic surface stabilization and Al2O3 deposition: Correlations between interface chemistry and capacitance measurements

Rôle de la zone interfaciale dans la qualité des proprietés électriques du système Al2O3/As$/\!\!/$InP

Passivation Of InP Using A Surface Science Approach: THE Al 2 0 3 /As//InP Case