摘要:

The effect of substrate temperature on the recrystallization of plasma chemical vapor deposition amorphous silicon films is investigated. The grain size of polycrystalline silicon films recrystallized at 600 °C increases as the substrate temperature decreases. The enlargement in the grain size is attributed to the decrease in the nucleation rate. The nucleation rate is suppressed by an increase in structural disorder of the Si network. Electrical properties of recrystallized films are improved by the increase in the grain size.

ISSN:0021-8979    

DOI:10.1063/1.346740

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An efficient preparation method, which provides wedge‐shaped cross‐section transmission electron microscopy samples, has been developed. It was then used to investigate the structure of as‐deposited cobalt multilayers on silicon substrates by rf plasma sputtering. It was found that an extended reaction takes place between Co and Si probably during the deposition. The cobalt atoms react with the silicon substrate to form an amorphous silicide layer. When the deposited layer is <3 nm thick, it entirely reacts with the substrate and can form an amorphous silicide as large as 5 nm. Above 4–5 nm thickness, growth of Co crystallites comes in competition with the formation of the amorphous silicide and limits it to 2 nm. The composition of this amorphous silicide is estimated to be Co2Si. In Co/C multilayers, the reactivity between the two materials is negligible, and the coalescence thickness of cobalt is 2–3 nm. At 2 nm, the cobalt layers are noncontinuous and very rough, whereas at 3 nm the critical thickness for crystalline nuclei coalescence has already been reached. The cobalt layers are then polycrystalline and have a reasonable roughness.

ISSN:0021-8979    

DOI:10.1063/1.346741

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

It is shown that high‐quality molecular‐beam epitaxial (MBE) regrowth of (Al,Ga)As on GaAs can be achieved by chemically passivating the GaAs surfaceexsituprior to regrowth with aqueous selenium reagents. Reflection high‐energy electron diffraction intensity oscillations show the bidimensional character of the regrowth and high‐resolution transmission electron microscopy reveals defect‐free regrown interfaces. Photoluminescence intensity from the Se‐treated GaAs surfaces on which Al0.5Ga0.5As is regrown rivals that from an allinsitugrown AlGaAs/GaAs interface. The high quality of these regrown interfaces could be attributed to the thermally and chemically stable selenium and oxygen phases that remain bound to GaAs under MBE conditions.

ISSN:0021-8979    

DOI:10.1063/1.346742

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We propose a means of constructing simplified quaternary phase diagrams based on a thermodynamic approach using known and estimated data for Gibbs free energy of formation. Isothermal, isobaric sections of the condensed phase diagrams are built up as tie lines, tie planes, and tie tetrahedra (representing two‐, three‐, and four‐phase equilibrium, respectively) in a regular tetrahedron. This extends the now well‐established methodology for ternary systems described, for instance, by Beyers [J. Appl. Phys.56, 147 (1984); Mat. Res. Soc. Symp. Proc.47, 143 (1985)]. The procedure is illustrated by reference to Ti‐Si‐N‐O, Al‐Si‐N‐O, Ti‐Al‐Si‐N and Ti‐Al‐Si‐O, systems which are relevant to interactions occurring at various interfaces during the formation of contacts in integrated circuits. These phase diagrams are then used to predict the stability of—or reactions in—metallization layers and thin‐film systems involving four elements. In addition, a method is suggested to estimate unknown free energies of formation from observations of thin‐film reactions and stability.

ISSN:0021-8979    

DOI:10.1063/1.346743

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

This paper presents high‐temperature effects on CoSi2/polycrystalline silicon (poly‐Si) bilayers, intended for metal‐oxide‐semiconductor gate applications. Both rapid thermal annealing and conventional furnace annealing were utilized for the investigation. At temperatures above 700 °C the structure breaks down due to silicon recrystallization within the silicide and simultaneous silicide growth into the polycrystalline silicon film. Recrystallized silicon adopts the silicide texture and this process terminates when the entire polysilicon layer is consumed. After completion the layer configuration is inverted, i.e., the silicide is adjacent to the gate oxide and covered with elemental silicon at the surface. This surface layer consists of large grains with few crystal defects, very different from the columnar structure of the as‐deposited silicon. With further annealing, grain growth in both phases continues, and each grain will ultimately extend from the oxide interface to the free surface. Lateral grain dimensions are typically a few times the total film thickness at this stage. Silicon recrystallization in the silicide layer can be suppressed if the polysilicon is doped with phosphorus prior to metal deposition, or the phenomenon can be alleviated by an arsenic or boron implantation into the silicide.

ISSN:0021-8979    

DOI:10.1063/1.346744

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The thermal activation of the capture coefficientcis very often treated in a semiclassical way, resulting from a simple energy barrier. Experimentally, this activation energyEbis said to be the slope of ln[c(T)] vs 1/TkT. Unfortunately, many experimental evidences deny this analysis and suggest that a single energy barrier is not enough to reproduce the physical behavior of a point defect. Here we propose a more complete approach to the problem of nonradiative carrier capture assisted by phonons, which is based on a less restrictive hypothesis and leads to a compact formulation of the capture coefficient. This formula reproduces the previous asymptotic forms at high temperature in the strong coupling limit, but remains valid over the whole temperature range and for any strength of the coupling between the lattice and the defect. This point is illustrated for typical cases and the accuracy of the new formula is shown in the case of the so‐called B level in GaAs, whose capture coefficient does exhibit a nonexponential behavior with temperature. Our wish is to put the theoretical point of view previously developed by Passler under a form allowing more extensive use in order to extract physical parameters from the experimentalc(T) curves with better accuracy.

ISSN:0021-8979    

DOI:10.1063/1.346745

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A scattering theory of one‐dimensional electron gas formed in a narrow channel GaAs‐AlGaAs high electron mobility transistor has been developed. The mobility values for the different scattering mechanisms have been computed and their variation with temperature has been presented. The various scattering processes include acoustic phonon scattering for both deformation potential and piezoelectric scattering mechanisms, impurity scattering, and surface roughness scattering at lower temperatures and polar optic phonon scattering at higher temperatures. The effect of dynamic screening has also been included. Finally, the temperature variation of thermopower for different 1D electron concentrations has been shown and attempts have been made to interpret the results obtained.

ISSN:0021-8979    

DOI:10.1063/1.346746

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A method for calculating impact ionization coefficients by solving the Boltzmann transport equation is presented. The distribution function is taken to be expressible as a Legendre polynomial expansion, which is substituted into a Boltzmann equation that incorporates the effects of nonparabolic band structure, deformation‐potential phonon scattering, and impact ionization. The resulting Boltzmann equation can be expressed in a linear form, and solved using sparse‐matrix difference‐differential methods. Ionization coefficients are obtained directly from the distribution function. Calculated values for the ionization coefficients agree very well with experiment for electrons in silicon.

ISSN:0021-8979    

DOI:10.1063/1.346747

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The anomalous behavior of forward and reverse bias current versus applied voltage in titanium‐silicided shallow source/drain junctions has been studied. The reverse leakage current characteristics inp+/nshallow junctions (Xj=130 nm) show that the current increases rapidly with titanium thickness and exponentially depends on the reverse bias voltage, while the activation energy of leakage current extracted from the temperature dependence of the current decreases with increasing reverse bias voltage. Forward current in a silicided junction is characterized at low temperatures for the first time. The ideality factor of the forward current increases as temperature decreases and has values higher than 2 at very low temperatures. This behavior cannot be explained by the field‐independent Shockley‐Hall‐Read generation‐recombination mechanism. A new mechanism involving the Frenkel–Poole barrier lowering of a trap potential is proposed.

ISSN:0021-8979    

DOI:10.1063/1.346748

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The piezoelectric photoacoustic effect of silicon wafers with ap/njunction in the dc electric field is studied experimentally and theoretically. Based on the transport properties of semiconductors, four kinds of thermal wave sources are considered: (i) instantaneous intraband nonradiative thermalization, (ii) interband nonradiative bulk recombination of photogenerated carriers (PGC), (iii) interband nonradiative surface recombination of PGC, and (iv) instantaneous Joule thermalization of PGC in the applied electric field. The theoretical results are in good agreement with those of experiment. Both show that the contribution of the Joule thermalization is a major factor and the photoacoustic signal will be strengthened as the dc electric field increases beyond an appropriate value. Therefore, the signal‐to‐noise ratio and the contrast of photoacoustic imaging of the semiconductor devices can be improved by the dc external electric field.

ISSN:0021-8979    

DOI:10.1063/1.347158

出版商:AIP    

年代:1990

数据来源: AIP