Electron affinity for intrinsic semiconductors

An approach for estimating the electron affinity using the method of dielectric formalism is developed. It is shown that the volume component of the electron affinity is related to the formation of exchange-correlation holes in the valence band. The interaction of an electron with this hole on the surface is responsible for the surface component. The relation obtained agrees satisfactorily with the rather meager experimental data available for semiconductors, and enables the electron affinity to be estimated for polycrystalline semiconductors for which there is no reference data. The calculation is carried out for 14 well-known semiconductors. In the case of metals, the relations obtained give the work function of the electron, which agrees, with a relative error of up to ±30%, with experimental data for the majority of elements.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 76–80, 1982.     

Electron work function of Rb-Cs alloys

The temperature and concentration dependences of the electron work function (EWF) of rubidium, cesium, and nine Rb-Cs alloys are studied by the Fowler photoelectric method under the conditions of an ultra-high vacuum. It is shown that the polytherms of the electron work function for the pure components and alloys decrease by a linear law with increasing temperature. Based on the experimental data obtained, it is concluded that the concentration dependence of the EWF for the binary Rb-Cs system has a linear (additive) character within the limits of experimental error (about 1%). The presence of the azeotropic point on the state diagram of the system is not visualized in the concentration dependence of the work function.     

Electron work function in alloys with alkali metals

The electron work function in alloys and compounds containing alkali metals, which are of interest for the designing of new photocathode materials and further development of the theory of electron emission, is studied. It is shown that a number of applied and theoretical issues in this field are poorly understood. These are the temperature and concentration dependences of the electron work function in binary metallic systems, the surface activity of components that are inactive in alloys with alkali metals, and some others.     

Electron propagation in magnetic semiconductors

A simple decoupling scheme is suggested and analyzed for the problem of the electron propagation in magnetic semiconductors treated in the s-d model. In most important cases, the method is shown to reduce to the Kubo form of the coherent potential approximation. It is then used to assess the role of higher order effects in the red shift of the optical absorption edge.     

Electron transport in disordered semiconductors

The density matrix of an electron in an amorphous semiconductor, written as a double path integral, is averaged over random disorder. For small disorder the golden rule result is recovered. When the mean disorder energy approaches k_BT, the electronic mobility goes to zero signalling disorder induced localization.     

Electron work function in alloys from the tin-lead system

The temperature and concentration dependences of the electron work function in Sn-Pb alloys are determined by the Fowler photoelectric method. It is shown that alloying of Sn with Pb decreases the electron work function rather than increasing it, as was reported in the literature. From the published data and experimental data obtained by the authors for the electron work function in the tin-lead system, it follows that the rate of decrease of the electron work function with increasing Pb concentration depends on the vacuum quality in the measuring cell and features in the electron work function isotherms are the more distinct the higher the vacuum.     

Conditions for theta-pinch experiments in intrinsic semiconductors

For small deviations from the intrinsic density the equations describing the theta-pinch in intrinsic semiconductors can be simplified. We get a condition for a noticeable compression effect in a suitable materials which is only determined by B_max and the compression-time T.     

Electron beam epitaxy of alloy semiconductors

Abstract

It was investigated that, when an Al evaporated layer on a GaP (GaAs, GaAs_1?y P _y ) substrate was bombarded with total fluences of 0.1?1.0 × 10¹⁸ electrons cm^?2 at 7 MeV and at 50°C, a thin heteroepitaxial layer of Al _x Ga_1?x P (Al _x Ga_1?x As, Al _x Ga_1?x As_1?y P _y ) crystal was grown on S-doped (111), (100) and (110) GaP [(110) Cr, O-doped GaAs, (100) Te-doped GaAS_1?y P _y ] substrates.

Evidence for the creation of the epilayers before annealing was obtained from measurements using an X-ray diffractometer, an X-ray photoelectron spectrometer, a reflection high-energy electron diffractometer, a transmission electron microscope and a scanning transmission electron microscope. In the case of Al/GaP, the epitaxial layers of Al_～0.25Ga_～0.75P, Al_～0.5Ga_～0.5P and Al_～0.75Ga_～0.25P were grown on (111), (100) and (110) GaP substrates, respectively. Their compositions did not vary with the total electron fluence.     

Electron work function of intermetallic compounds in the cerium-cobalt system

The concentration dependences of the electron work function for lithium samples in the cobaltrich region of the state diagram of the Ce-Co binary mixture is studied by the contact potential difference method at 20°C. It is shown that the electron work function isotherm has the shape of a broken line with kinks corresponding to intermetallic compounds formed in the cerium-cobalt binary system.     

The electronic work function of the different faces of tungsten

We present a semi-empirical theory of the electronic work function of the different faces of tungsten. All the parameters entering the theory, except one, are estimated independently. The one adjustable parameter relates to the isotropic contribution to the work function, and, can, in principle, be determined from a self-consistent calculation of the band-structure of the energy levels in the bulk of the metal. The calculated values for the work function are in reasonably good agreement with available experimental data for practically all of the crystallographic planes with the exception of the (100) plane. For the latter, the calculated value is 0.3 eV above the experimental value. It is suggested that a negative contribution to the surface dipole potential from surface states, that exist on this plane, may be the reason of this discrepancy.     

Electron capture cross-section in covalent semiconductors

The energy dependence of the differential capture cross-section for the free carriers in a covalent semiconductor is obtained by a numerical method adopting the Abakumov-Yassievich model [1] for the process of recombination. The result is essentially required for a theoretical study of the electrical transport and other related phenomena in semiconductors at low lattice temperatures.     

Electron states in diluted magnetic semiconductors

One of the remarkable properties of the II–VI diluted magnetic semiconductor (DMS) quantum dot (QD) is the giant Zeeman splitting of the carrier states under application of a magnetic field. This splitting reveals strong exchange interaction between the magnetic ion moment and electronic spins in the QD. A theoretical study of the electron spectrum and of its relaxation to the ground state via the emission of a longitudinal optical (LO) phonon, in a CdSe/ZnMnSe self-assembled quantum dot, is proposed in this work. Numerical calculations showed that the strength of this interaction increases as a function of the magnetic field to become more than 30 meV and allows some level crossings. We have also shown that the electron is more localized in this DMS QD and its relaxation to the ground state via the emission of one LO phonon is allowed.     

Large intrinsic birefringence in zinc-blende based artificial semiconductors

A new attempt to solve the phase matching problem for semiconductor-based frequency conversion devices, based on the implementation of intrinsic birefringence in artificial materials, is discussed. The first results concerning the growth and characterization of ultrashort period superlattices are presented. To cite this article: J.-M. Jancu et al., C. R. Physique 8 (2007).     

Optical detection of quantum geometric tensor in intrinsic semiconductors

Quantum geometric tensor, including a symmetric real part defined as quantum metric and an antisymmetric part defined as Berry curvature, is essential for understanding many phenomena. In this study, we investigated the photogalvanic efect of semiconductors with time-reversal-invariant and spatial inversion symmetries using the quantum kinetic equation. We concluded that the integral of the symmetric(antisymmetric) part of quantum geometric tensor on the equal energy surface in momentum space, satisfying the resonance condition, is related to the generation rate of carriers in semiconductors under linearly(circularly) polarized light. Under additional bias voltage, the dc photocurrent is proportional to the bias voltage. Our study provided an alternative interpretation for the photogalvanic efect in the view of quantum geometric tensor. Additionally, it classified the intrinsic diference between linearly and circularly polarized optical fields.     

Stage iv work hardening of metals and semiconductors

The work hardening rate of metals in stage IV is analysed in the two-phase model of Nix et al. assuming dynamic recovery by cross slip but no climb which describes stage IV in semiconductors.