Interfacial Electrical Properties Research Articles

Electrical properties of p-type HgCdTe/ZnS interfaces

A study is made of <i>p</i>-type HgCdTe surface passivation with ZnS. Measurements of capacitance-voltage characteristics for metal insulator semiconductor (MIS) devices show that the interface electrical properties strongly depend on the surface preparation. Under some appropriate surface pretreatment, the fixed interface charge density can be lowered to near -1 x 10¹¹ cm^-2, and the slow trap density can be less than 1 x 10¹¹ cm^-2, but the interface trap density is still as high as 10¹² cm^-2 eV^-1. Experimental results are discussed.

Nitrogen-Atom Bonding at SiO2/Si Interfaces in Metalinsulator-Semiconductor (MIS) Stacked Gates Made by Integration of Plasma Assisted Oxidation-Deposition and Rapid Thermal Processing

ABSTRACTSiO2 thin films were deposited by remote PECVD on Si surfaces exposed to species generated in O2/N2 and O2/NH3 plasmas. The surface chemistry was studied by Auger Electron Spectroscopy, AES, and the electrical properties of the SiO2/Si interface by high frequency and quasi-static Capacitance-Voltage, C-V, measurements. The AES results showed that Ccontamination was removed by exposure to both plasma-excited gas mixtures, but that N-atoms were incorporated into the SiO2 film, and Si-N bonds were formed at the SiO2/Si interface. C-V measurements indicated that the Si-N bonding structure, rather than the N-atom concentration, is critical in determining the interface electrical properties. The effects of Rapid Thermal Annealing, RTA, on the electrical properties of these SiO2/Si interfaces were also studied.

Correlation of the interfacial structure and electrical properties of epitaxial silicides on Si

The Schottky barrier height (SBH) measured at epitaxial NiSi2 contacts is shown to be strongly influenced by the local interfacial structure. Diodes with guard rings, which eliminate the edge leakage current which has hampered some previous studies, were prepared by molecular-beam epitaxy of NiSi2 films on a wide range of n- and p-type doped Si substrates. Schottky diodes processed with high quality NiSi2 films on Si(111) are shown to exhibit highly ideal electrical properties. Structural inhomogeneity at the NiSi2/Si(100) interface is shown to lead to electrical properties which are consistent with the existence of spatial inhomogeneity in the SBH. Numerical simulations of the electron transport across the inhomogeneous diodes, based on a spatial variation of the interfacial SBH consistent with the observed structural inhomogeneity in the films, are shown to accurately reproduce the trends in the electrical behavior of the inhomogeneous diodes. The necessity to understand the interfacial atomic structure at metal/semiconductor contacts in order to understand the formation mechanism of the Schottky barrier is stressed by these results.

Growth of passivating UV/ozone oxides on InP: Correlations between chemical composition and interfacial electrical properties

Native oxides grown on InP by UV/ozone oxidation are studied as a function of various experimental conditions. They are compared to standard InPO 4 thermal oxides and to In(PO 3) 3 anodic oxides. The chemical composition of these oxides is investigated by X-ray photoelectron spectroscopy. The atomic composition of the UV oxides varies from InP 0.3O 2.25 to InP 0.8O 3.5 as a function of the growth conditions. It is shown that these phosphates have a well-defined local order. The electrical properties of the oxide-InP interfaces are studied using Schottky diode barrier ( I–V) measurements on metal/thin-oxide/semiconductor (MIS) structures. A correlation between chemical composition and interfacial electrical properties is established.

Kinetic and interface studies for MOCVD CdTe and HgCdTe epilayers grown on GaAs substrates

The growth rates of CdTe and CMT on GaAs and on CdTe/GaAs substrates were studied as a function of temperature and gas composition. A Langmuir-Hinshelwood model for surface reaction control region is proposed. The CdTe/GaAs interface was examined by X-ray double crystal diffraction, laser Raman spectroscopy and transmission electron microscopy (TEM). A defect layer was observed at CdTe/GaAs interface. The relationship between the interface qualities and electrical properties of the CMT overlayers was discussed.

Electrical characterization of reoxidized nitrided silicon films on silicon

Thin oxynitride layers in the range of 50–100 Å thickness were grown by the oxidation of a thermally nitrided silicon surface. The interface electrical properties were investigated and related to the film composition. Similar values to those observed in standard oxides were obtained for the density of interface states, the surface generation velocity, and surface mobility for those layers having the highest oxidation resistance.

Substrate temperature dependence of subcutaneous oxidation at Si/SiO2 interfaces formed by remote plasma-enhanced chemical vapor deposition

We have previously reported that subcutaneous oxidation reactions between process gases and Si surfaces occur during deposition of thin films of SiO2 by remote plasma-enhanced chemical vapor deposition (remote PECVD) [G. G. Fountain, S. V. Hattangady, R. A. Rudder, R. J. Markunas, G. Lucovsky, S. S. Kim, and D. V. Tsu, J. Vac. Sci. Technol. A 7, 576 (1989) and G. Lucovsky, S. S. Kim, D. V. Tsu, G. G. Fountain, and R. J. Markunas, J. Vac. Sci. Technol. B 7, 861 (1989)]. We find that the rate of this oxidation process is substrate temperature (Ts) dependent, increasing with increasing Ts. The rate of SiO2 deposition by remote PECVD decreases with increasing Ts and the combination of oxide deposition and subcutaneous oxidation serves to establish limits on the deposition temperature, and oxide thickness for gate-quality SiO2 films on cleaned and characterized Si surfaces. This paper describes the subcutaneous oxidation process, the nature of the oxide films, and the effects of subcutaneous oxidation on interfacial electrical properties of the Si/SiO2 interfaces in metal–oxide-semiconductor (MOS) structures.

Interfacial microstructure and electrical properties of the Pt/Ti ohmic contact in p-In0.53Ga0.47As formed by rapid thermal processing

The interfacial microstructure and electrical properties of the Pt/Ti ohmic contact to p-In0.53Ga0.47As (Zn: 5×1018 cm−3) formed by rapid thermal processing (RTP) were intensively studied. Significant interdiffusion of Ti, In, and As across the interface, driven by RTP, occurred at temperatures of, or above, 350 °C for a heating duration of 30 s. A minimum specific contact resistance (9.0×10−6 Ω cm2) was achieved after heating at 450 °C. Cross-sectional transmission electron microscopy of this sample revealed an interfacial reaction zone with complicated microstructure, and the dominant interfacial compound was identified to be InAs. Further increase in RTP temperature resulted in a change in the microstructure, and degradation of the contact resistance. The temperature-dependence characteristic of the specific contact resistance of as-deposited Pt/Ti contact to InGaAs revealed a thermionic-emission-dominated carrier-transport mechanism with an effective barrier height φb, of 0.13 V. RTP treatment to the sample at elevated temperatures up to 450 °C decreased the temperature dependence of the contact resistance. This phenomenon strongly suggests a partial conversion of the dominant carrier-transport mechanism across the contact area from thermionic emission to field emission. This was further verified by fitting the temperature dependence of the measured contact resistance to a phenomenological theory based on a linear combination of the two different types of carrier-transport mechanisms operating at isolated area segments distributed uniformly across the interface.

HgTe/HgCdTe superlattices: Growth, electrical and optical properties

HgTe/HgCdTe superlattices are under development as a new infrared material for long wavelength IR applications. We report the molecular beam epitaxial growth of high quality HgTe/HgCdTe superlattices and the dependence of interface quality, electrical properties, and optical properties on growth conditions. Growth at 170°C on (100) substrates produced excellent quality superlattices based on these criteria. Hall measurements indicated high n- and p-type mobilities and the absorption spectra exhibited step-like features characteristic of layered structures and in agreement with theory. Raman and magneto-optical measurements have also been done in order to characterize the superlattice.

.ZETA.-potential and surface dyeability of grafted nylon 6 fibers in aqueous solution of methylene blue.

To study the interfacial electrical properties of the nylon 6 fibers grafted with acrylic and methacrylic acid and the surface dyeability of cationic dye on these fibers, the ζ-Potential of the fibers was measured in the aqueous solution of Methylene Blue. With an increase in the concentration of the dye, the sign of the ζ-potential changed from negative to positive and the amount of the dye adsorbed on the fiber surface increased. These results suggest that electrostatic interaction and van der Waals force act between the fibers and the dye. The amount of the adsorbed dye decreased with an increase in the degree of grafing.The free energy of adsorption (Δ_??_) of Methylene Blue on the fibers was calculated from the slope of the ζ-log Cd (Cd: the concentration of dye) curve etc. The negative value of Δ_??_ decreased with an increase in the degree of grafting. The heat of adsorption (Δ_??_) was negative and the entropy of adsorption (Δ_??_) was positive. The positive value of Δ_??_ suggests the importance of entropic interaction (the formation of hydrophobic bond) as a driving force to the adsorption of the dye on the fiber surface. The negative values of Δ_??_ of the ungrafted and the grafted nylon 6 fibers were larger than those of the ungrafted and the grafted polyester fibers, and the Δ_??_ values of the former were smaller than those of the latter documented in our recent report. Therefore, the dependence of hydrophobic bond on the ungrafted and the grafted nylon 6 fibers was smaller than that on the ungrafted and the grafted polyester fibers. It is concluded that the surface dyeability of Methylene Blue on the grafted nylon 6 fibers is lower than that on the ungrafted nylon 6 fiber, because the water-soluble polymer layer is formed at the fiber surface due to the grafted polymer chains.

Stable Solid-Phase Ohmic Contacts to n-GaAs with Diffusion Barriers

ABSTRACTContacts to GaAs substrates with n-type epilayers formed by GaAs/Ni/Ge/WN/Au, GaAs/Ni/Ge/Ni/WN/Au and GaAs/Ge/ Ni/WN/Au systems were investigated. Ohmic contacts in these systems were formed by a solid-phase reaction between Ni/Ge and GaAs. Interfacial reaction and electrical properties of these contacts are characterized by backscattering spectrometry, transmission electron microscopy and contact resistivity measurements. Resistivities in the 10−δ Ω cm range are achieved.

Interfacial electrical properties of grafted nylon 6 fibers.

Interfacial electrical properties of the surface of nylon 6 fibers ungrafted and grafted with acrylic and methacrylic acid were investigated. The isoelectric point (ζ=0) shifted into acidic side with increase in the amount of grafting.In neutral and alkaline solution, saturated values of ζ-potential of fibers decreased with increase in the amount of grafting. Stern potential (φδ) and the position (t) of slipping plane in the electric double layer of the fiber surface were estimated. φδ of grafted fibers decreased with increase in the amount of grafting and the value of t for grafted fibers was greater than that for ungrafted fiber.It was suggested from these facts that the grafted nylon 6 fiber swelled remarkably in solution and that the hydrogel layer was formed at the surface by grafting of the fiber surface.

A learning mechanism for the identification of hidden structures in signal sets: [formula omitted]. Center for Neural Science and Division of Applied Mathematics, Brown University, Providence, Rhode Island, 02912

2D/3D perovskite heterostructure can combine the advantages of 2D perovskite with well stability and 3D perovskite with high efficiency. 2D BA2PbI4/3D MAPbI3 heterostructures are constructed to study the interfacial electrical properties and charge transfer characteristics by first-principle calculations. 3D MAPbI3 perovskite have two kinds of contacting interface, i.e., PbI interface and I interface. The 2D/3D interface heterostructures are van der Waals contacting, and their light absorption can be enhanced as compared to pure 2D or 3D perovskite, mainly resulting from 3D perovskite part in the heterostructure. In 2D/I interface heterostructure, the band gap is 1.15 eV, and the charge recombination center is at 2D BA2PbI4 interface, which favor to improve the power conversion efficiency (PCE). While in 2D/PbI heterostructure, the band gap is as small as 0.53 eV, and the charge recombination center is at PbI interface, leading to a large number of recombination and low PCE. The work function difference of 2D BA2PbI4 and 3D MAPbI3 perovskite is the nature of energy level shifting and interface charge oriented movement. These results demonstrate that the construction of 2D BA2PbI4 and 3D I interface heterostructure by interfacial engineering is a potential strategy to enhance the performance of the 2D/3D heterostructured PSCs.

Characterization of interface electrical properties in SiO 2/InSb metal/insulator/semiconductor structures prepared by plasma-enhanced chemical vapour deposition

The preparation of dielectric layers possessing good insulating and interface properties is most important for metal/insulator/semiconductor applications. This problem presents a considerable challenge in the case of narrow gap semiconductors. In this paper we report on the electrical properties of metal/insulator/ semiconductor structures produced on p-InSb(111) by plasma-enhanced chemical vapour deposition of SiO 2. The interface electrical properties are characterized by low and high frequency capacitance-voltage techniques in the temperature range 4.2–77 K. An appropriate theoretical model is employed for evaluation of the experimental data in which the non-parabolicity of the InSb conduction band, the incomplete ionization and recharging of dopants and the degenerate statistics are taken into account. The applicability of plasma-enhanced chemical vapour deposition for metal/insulator/semiconductor device preparation on InSb is demonstrated.

Propriétés physiques des structures MIS réalisées sur InP(n) en utilisant un oxyde bicouche comme isolant

The interfacial electrical properties of an RF plasma grown native oxide double-layer have been studied. These measurements include capacitance and conductance versus bias voltage with frequency and temperature as parameters. We find that the electrical characteristics of the MIS diodes depend on the sample and time of oxidation. The capacitance-voltage data performed at different frequencies and temperatures show an unusual behaviour, namely, a plateau in negative gate bias and some frequency and temperature dependence in the entire range of the applied forward gate bias. The surface composition and stoichiometry of oxides grown on InP by using the InP or alumina-cathode have been examined by using XPS technique. The XPS results show that the oxide layers are depleted of phosphorus and appeared to be indium-rich oxides.

New native oxide of InP with improved electrical interface properties

The electrical properties of InP insulator interface were improved by using a new native oxide between gate insulator and the semiconductor. This phosphorus-rich oxide identified as In(PO3)y polyphosphate was grown anodically. Capacitance-voltage measurements on this metal-insulator-semiconductor structure yielded an interface state density as low as 4×1010 cm−2 eV−1 and were nearly free of hysteresis in the depletion and accumulation region.

Interface effects of SIPOS passivation

Electrical characterization of metal-semi-insulating polycrystalline silicon (SIPOS)-Si samples have been carried out using IV , C-V , and C-t techniques. Bulk resistivity and interface properties have been examined. The results indicate that annealing can give rise to a current barrier at the SIPOS-Si interface that constitutes another mechanism for interface charge formation as distinct from interface states. This current barrier-induced interface charge can lead to significant spreading of the depletion zone on test diodes. With SIPOS bulk resistivity greater than 108Ω . cm, the interface electrical properties are shown to have greater influence than bulk SIPOS properties on device behavior.

Interfacial electrical properties of electrogenerated bubbles

Electrophoresis measurements on bubbles of electrogenerated hydrogen, oxygen and chlorine rising in a lateral electric field, are reported. In surfactant-free solutions, all bubbles displayed a point of zero charge of pH 2–3, i.e. they were negatively charged at pH > 3 and positively charged at pH < 2. The bubble diameter and electric field strength dependence of the electrophoretic mobilities, coupled with bubble rise rate measurements, indicated that the gas—aqueous solution interface was mobile, such that classical electrophoresis theory for solid particles could not be applied. Adsorption of anionic or cationic surfactants, in addition to modifying the apparent bubble charge, also tended to rigidify the bubble surface, so that at monolayer coverage the bubbles behaved as solid particles.

Quantitative Analysis of the Interfacial Barrier to Membrane Transport of Cholesterol Solubilized in a Charged Micellar System

The transport of cholesterol solubilized in polyoxyethylene(10)-nonylphenol ether with benzyldimethyltetradecylammonium chloride additive (4:1, w/w) was studied in a diffusion cell separated by a silicone rubber membrane. Overall kinetics revealed the presence of an interfacial barrier. Additions of NaCl or Na2SO4 abolished the barrier to the extent that total cholesterol flux was essentially limited by membrane diffusion considerations. The results are consistent with the concept of micelles diffusing in an electrical field followed by a collision-complex transfer of cholesterol in the aqueous–membrane interfacial region. The electrostatic force of repulsion arises from the overlap of diffuse electrical double layers emanating from the charged mixed micelle and the cationic surfactant adsorbed on the membrane. The influence of surfactant concentration on cholesterol transport kinetics was consistent with electrostatic phenomena. The derived physical model focused on interfacial electrical properties in the donor chamber by maintaining a high concentration (≥0.1 M) of strong electrolyte in the receiver. A linear regression of the logarithm of theoretical transport resistance, total resistance less membrane and receiver boundary layer resistances, versus (ionic strength)1/2 in the donor resulted in a reasonable estimate of the total surface potential of the micelle and membrane surfaces as well as the net dispersion attraction constant.

Effects of H2O on the SiO2-HgCdTe interface

The effects of water on the electrical and mechanical properties of the PhotoxTM-HgCdTe interface were investigated using capacitance-voltage techniques (1 MHz an quasi-static) and a simple scratch test, in conjunction with Fourier spectroscopy to monitor actual water content. PhotoxTuM is a form of SiO2 deposited by a low-temperature (&amp;lt;100 °C) chemical vapor reaction. The water which is available as a byproduct of the deposition reaction becomes incorporated in the layer, with the amounts depending on deposition rate, as SiOH, H2O, and SiH...O It is seen that SiH increases with rate while SiOH and H2O decrease. After long periods (1 year) of atmospheric exposure, the SiH concentration goes to zero. In fact, layers deposited at higher rates in some ways come to spectrally resemble the lower deposition rate layers. The increased SiOH concentrations of the lower deposition rate layers result in better mechanical integrity of the interface. These rate-dependent concentrations do not affect interface electrical properties. However, it was seen that water absorbed after the layer was deposited strongly affected electronic structure, increasing interface state density between the valence band and midgap and increasing the net interface charge by up to +1×1011 cm−2. These effects are reversible with the initial interface structure recovered after a low-temperature vacuum bake.