摘要:

Diffusing species in the reaction of thin tungsten films with aluminum overlayers in vacuum have been investigated by marker experiments using Rutherford backscattering spectrometry and scanning electron microscopy techniques. It has been found that Al was the dominant diffusing species in the reaction. Ni has been used as the marker material. Samples with both pure and Al‐diluted and both unburied and buried Ni markers at the interface of thin W films and Al overlayers have been studied to compare barrier effect of the markers. Our results showed that the Ni‐based markers do not impede the reaction of thin W films with Al overlayers.

ISSN:0021-8979    

DOI:10.1063/1.345413

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An inconsistency between commonly used values of the silicon intrinsic carrier concentration, the effective densities of states in the conduction and valence bands, and the silicon band gap is resolved by critically assessing the relevant literature. As a result of this assessment, experimentally based values for the valence‐band ‘‘densities‐of‐states’’ effective mass are determined in the 300–500 K range and are shown to be in good agreement with recent theoretical calculations. At 300 K, experimentally based values of 3.1×1019cm−3for the valence‐band effective densities of states and 1.08×1010cm−3for the intrinsic carrier concentration are determined. Although in good agreement with theoretical calculations, these are significantly higher and lower, respectively, than commonly used values in the past. These results have important implications in the calculation of other silicon material and device parameters.

ISSN:0021-8979    

DOI:10.1063/1.345414

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A Monte Carlo procedure to simulate the penetration and energy loss of low‐energy electron beams through solids is presented. Elastic collisions are described by using the method of partial waves for the screened Coulomb field of the nucleus. The atomic charge density is approximated by an analytical expression with parameters determined from the Dirac–Hartree–Fock–Slater self‐consistent density obtained under Wigner–Seitz boundary conditions in order to account for solid‐state effects; exchange effects are also accounted for by an energy‐dependent local correction. Elastic differential cross sections are then easily computed by combining the WKB and Born approximations to evaluate the phase shifts. Inelastic collisions are treated on the basis of a generalized oscillator strength model which gives inelastic mean free paths and stopping powers in good agreement with experimental data. This scattering model is accurate in the energy range from a few hundred eV up to about 50 keV. The reliability of the simulation method is analyzed by comparing simulation results and experimental data from backscattering and transmission measurements.

ISSN:0021-8979    

DOI:10.1063/1.345415

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electrical transport properties of Au‐dopedp‐type polycrystalline silicon have been investigated by using the electrical resistivity and Hall mobility measurements. It has been found that the specific resistivity increases with decreasing annealing temperature and Hall mobility decreases with decreasing the effective carrier (hole) concentration, in contrast to the normal result for the single‐crystal specimen. A simple physical interpretation of these results is also given.

ISSN:0021-8979    

DOI:10.1063/1.345416

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Accurate rates computed for electron‐hydrogen scattering are applied to intravalley scattering of electrons by neutral hydrogenic donors in moderately doped semiconductors (at low compensation) held at cryogenic temperatures. The differential rates for both elastic and impact‐excitation scattering are included explicitly. In contrast to the traditional assumption of exclusively isotropic elastic scattering, we show that the elastic scattering strongly favors the foward directions for energies well below impurity ionization. Near the impurity ionization energy, the inelastic impact excitation ignored in traditional treatments accounts for about 10% of the total impurity scattering rate and dominates impurity scattering for higher energies. Inelastic scattering strongly favors the forward directions for all energies. The consequences of both anisotropic and inelastic scattering for hot‐electron transport are demonstrated in a sample calculation for a Si:As layer subject to an electric field. In particular, the threshold for non‐Ohmic transport is found at much lower field strengths in calculations employing our proposed neutral‐impurity scattering rates than in calculations employing an extrapolation of the traditional isotropic elastic rate.

ISSN:0021-8979    

DOI:10.1063/1.345417

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The carrier transport in poly(phenylmethylsilane) films doped with trap‐forming organic compounds with different ionization potentials has been investigated. The carrier transport in the doped systems is discussed as trapping events in the transport‐active host polymer. Zero‐field activation energyE0corresponds well to the ionization potential difference between the additives and host polymer. The field and temperature dependencies of the mobilities have been analyzed in the framework of Gill’s [W. D. Gill, J. Appl. Phys.43, 5033 (1972)] expression. Its characteristic parameterT0, at which the field dependence disappears, has been found to depend on trap depth and concentration, and an explicit expression interrelating them has been experimentally derived.

ISSN:0021-8979    

DOI:10.1063/1.345418

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The low‐temperature impact ionization avalanche breakdown inp‐Ge is investigated on a series of samples with various lengths of the electrically active region located between the ohmic contacts. We have studied the breakdown behavior as a function of the contact distance together with the response to an applied magnetic field. A simple model considering the specific hot‐carrier situation in the prebreakdown regime can explain the experimental results.

ISSN:0021-8979    

DOI:10.1063/1.345419

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Several ferroelectric thin films withn‐type orp‐type conductivity, including undoped and doped lead zirconate titanate, barium titanate, strontium barium niobate, and potassium niobate, as well as lead barium niobate, were made on silicon single‐crystal substrates by the sol‐gel process. Self‐biased heterojunction effects were observed in bothp‐ferroelectric thin film onn‐silicon andn‐ferroelectric thin film onp‐silicon by the measurement of current‐voltage characteristics. It has been observed that eitherp‐njunction orn‐pjunction in the ferroelectric‐semiconductor systems behave like a rectifying diode. However, the junction effect is weak in thep‐ferroelectric thin film onp‐silicon system. A physical model based on the consideration of energy‐band theory has been constructed in explaining this effect. Possible applications of this effect are discussed.

ISSN:0021-8979    

DOI:10.1063/1.345420

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

As insulated gate field effect transistor dimensions continue to decrease, and fabrication sequences rely increasingly on processes that involve ionizing radiation, it becomes essential to understand the radiation‐induced threshold voltage shift (&Dgr;VT) dependence on gate‐insulator thickness (tox), since threshold voltage tolerances are required to scale with device dimensions. In the present study,n‐channel insulated gate field effect transistor devices were fabricated with gate‐insulator thicknesses ranging from 6–50 nm, and were then exposed in an unbiased state to AlK&agr; x‐ray radiation to simulate process‐induced ionizing radiation exposure. Gate‐oxide Coulombic defects and neutral electron traps were measured before and after irradiation using optically assisted electron injection. Following irradiation and injection, the measured voltage shifts indicated that the ‘‘extrinsic’’ defects are localized near, but not at, the Si/SiO2interface. For oxide thicknesses where the top gate electrode lies in the region above the extrinsic defect volume &Dgr;VTis found to be linear intox; at thicknesses where the top gate electrode encroaches upon the defect region, &Dgr;VTis found to be quadratic intox, and for very thin oxides, &Dgr;VTis observed to approach zero. A defect distribution model that applies to process‐induced radiation exposure is formulated to explain this behavior. This model also provides a unique and simple method for determining the defect centroid in gate insulators that have been exposed under such irradiation conditions.

ISSN:0021-8979    

DOI:10.1063/1.345421

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The microstructure and electrical properties of the contacts formed in the Ti(30 nm)/Al(10 nm)/⟨100⟩p‐type Si system due to rapid thermal processing at temperatures between 300 and 800 °C were studied extensively. An eutectic melting, initiated at the Al/Si interface, was already observed after 2 s at 580 °C. This rapid melting, which was first observed by the authors in the Ni/Al/Si system, resulted in the formation of a Al3Ti(20 nm)/Ti7Al5Si12(5 nm), epi‐TiSi2(45 nm)/p‐type Si layered structure with smooth interfaces. The TiSi2layer grew epitaxially on the ⟨100⟩Si substrate with the following relationships: (101)TiSi2(C54)∥(001)Si and [151]TiSi2(C54)∥[220]Si. The melting reaction influenced the sheet resistance and the Schottky barrier height of the formed contacts, which decreased from 0.67 to 0.49 eV at 580 °C. The correlation between the electrical properties and the microstructure of the contacts formed in the Ti/Al/Si system due to the rapid thermal processing is discussed in comparison with the Ni/Al/Si system.

ISSN:0021-8979    

DOI:10.1063/1.345422

出版商:AIP    

年代:1990

数据来源: AIP