Phenomenological model of the diffusion of impurity atoms in ultrathin silicon layers with a nonuniform distribution of temperatures

The influence of fluxes of intrinsic nonequilibrium semiconductor defects on impurity diffusion in a nonuniform temperature field is considered in the framework of the phenomenological theory of irreversible processes. The mass transfer coefficient defined as the ratio of the concentrations of nonequilibrium and equilibrium defects is introduced to take the excessive concentration of nonequilibrium defects into account. The introduction of this coefficient into equations for matter and heat fluxes makes it possible to express the parameters of the process of thermal diffusion (the diffusion coefficient and the heat of transport) as a time-dependent function of the excessive concentration of intrinsic nonequilibrium semiconductor defects.     

On an estimate of the piezoresistance coefficients in diffusion layers taking account of a two-dimensional impurity distribution

The influence of finite diffusion layer width on its piezoresistance coefficient is analyzed in this paper. It is shown that a diminution in the width results in growth of the absolute value and temperature dependence of the fundamental piezoresistance coefficients.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 42–46, September, 1977.     

Percolation mechanism of the diffusion of impurity atoms in dense surface layers

The molecular dynamics method is used to study the migration of an impurity atom on an unfilled square lattice. The calculations are performed on a lattice containing 2¹² × 2¹⁴ sites at various values of the ratio p of the frequencies of jumps impurity and lattice atoms and various relative concentrations of vacancies ? _V . In the limit of vanishingly small concentrations of vacancies, ? _V ? 1, the present simulation results are in agreement with our previous analytical results. With increasing ? _V , the diffusion coefficient of impurity atoms predicted by the simulations exceeds the result of the analytical theory, a behavior that can be explained by the growing influence of vacancy clusters, voids on the surface, in which the impurity atom can travel long distances. This is most clearly seen in the case of highly mobile impurity atoms (p ? 1), where within the characteristic time of displacement of impurity atoms, lattice atoms remain practically immobile, and the problem appears to be closely related to the percolation problem. In this case, up to ? _V ≈ 0.3, the diffusion coefficient is independent of p; then, such a dependence appears, and the diffusion coefficient increases sharply with ? _V .     

Effect of orthohydrogen impurity on the absorption intensities of single transitions in a solid parahydrogen crystal

This paper provides insights for the accurate calculation of theoretical intensities of single transitions in a parahydrogen crystal containing trace amounts of orthohydrogen impurity. From the ratio of the experimental intensity to that of theoretical one we can deduce the value of the phonon renormalization factors, which are not easily amenable for calculations, a priori and are customarily set equal to unity. The ratio for S transitions varies over a wide range from 0.15 to 0.94. Different reasons are advanced for this wide variation and remedy suggested. A more careful experimental measurement of the intensity of single transitions in a parahydrogen crystal at different, carefully controlled, orthohydrogen concentrations is desirable. The accurate knowledge of the ratio will then lead to a detailed understanding of the theory of phonon renormalization factors in quantum solids.     

含双负缺陷的一维光子晶体耦合腔的杂质带特性

利用转移矩阵方法研究了含双负缺陷的一维光子晶体耦合腔的透射谱.计算结果表明，如果改变缺陷的折射率，缺陷模之间的耦合作用将发生改变，使得能隙中的杂质带也随之改变.若这个折射率取适当值，则可以在禁带中同时出现几个尖锐的透射峰和较宽的通带，这种结构可同时用于多通道窄带滤波和宽带滤波. 关键词： 光子晶体 缺陷模 杂质带 滤波     

Numerical method for determining the diffusion coefficient of a gas-forming impurity in a solid using the results of the integral penetrability method

A numerical method is proposed for determining the diffusion coefficient of a gas in a solid upon its isothermal penetration through a plane-parallel plate and accumulation in a closed receiving volume. The method is tested with the use of mathematical modeling as well as on a specific experimental material.     

单晶固体中正电子波函数的计算

介绍了正电子波函数计算的两种基本方法——有限差分方法(FDM)与平面波方法(PW).并以单晶Si为例,计算出正电子的波函数,从而计算出正电子在Si中的密度分布,由该正电子密度,进一步计算出了正电子在Si中的体寿命.计算结果与我们最近的实验结果(220 ps)符合得很好.最后,探讨了这两种方法各自的优缺点.     

Analysis of impurity distribution in n-GaAs layers by photoconductivity and cyclotron resonance measurements

High-purity GaAs layers of 8 to 80 μm thickness on semi-insulating substrates have been investigated. From the 1s-2p transition of shallow donors the dopants are identified and the exact transition energies determined.

Using the relation Δω √N_I from cyclotron emission measurements the total ionized impurity density N_I was determined. In homogeneous samples a good agreement between the impurity density determined from the cyclotron resonance linewidth with total impurity density values obtained from Hall mobility data is found.

The photoconductivity and transmission measurements show the same linewidth on impurity dependence for the different types of shallow donors.     

Mobility of 2D-electrons in scattering on a correlated distribution of impurity ions in doped thin layers

The spatial correlations of impurity ions in doped thin layers have been considered. A model of hard spheres on the plane has been developed for describing the correlations. In this model, an analytical expression has been obtained for the structure factor of 2D-electrons. The concentration dependences of the mobility of 2D-electrons in heterostructures with separate doping have been investigated using Al _x Ga_{1 − x} As/GaAs as an example.     

Theory of an impurity state in a crystal

A review is given of the theory of the effects of single-, or low-concentration impurities on the properties of otherwise perfect crystals. The subjects considered include electron density, anomalies in the temperature dependence of the spontaneous magnetization of a ferromagnetic insulator and the spectrum of lattice vibrations. All the problems are considered from a single mathematical point of view in which the approximation of localized perturbations and Green function techniques are used. The conditions for the occurrence of localized and virtual states are discussed. The review concludes with a formulation of the general methods of the theory.     

Diffusion of a low-soluble impurity in a solid matrix

An analytical expression for the concentration profile of a low-soluble diffusant in a sample is derived for a high-capacity diffusion source. The model is checked by determining the diffusion coefficient of yttrium in beryllium.     

Self-correlation functions for impurity diffusion in hexagonal lattices

Long-range diffusion of the substitutional impurity in the otherwise monoatomic hcp-like lattices (H1 type) via the monovacancy mechanism has been considered within the encounter approximation. A five-frequency model (valid for cubic lattices) extends here naturally into a sixteen-frequency model, leaving fourteen normalized frequencies, the latter describing an anisotropic part of the self-correlation function. Two simplified cases can be distinguished: a self-diffusion being described by a single normalized frequency and a true hcp lattice, where only three normalized frequencies remain independent of each other. A general formalism is discussed and a few examples are evaluated numerically.     

Self-correlation functions for impurity diffusion in cubic lattices

Hyperfine Interactions - Radial parts of the spatial self-correlation functions for a long-range diffusion of an isolated impurity via the monovacancy mechanism have been calculated for the...     

Diffraction of X-ray spatially inhomogeneous beam in a crystal with cubic nonlinearity

Diffraction of a spatially inhomogeneous X-ray wave was theoretically studied in a crystal with cubic nonlinear response to the strength of an external electric field. Using numerical calculations in case of two-beam diffraction of a narrow incident beam, the intensity distributions on the output surface of the crystal was investigated depending on the thickness and intensity of the incident beam. The results of numerical calculations of integral (spatial) coefficients of transmission and reflection are given as functions of incident wave intensity for fixed thickness of the crystal.