Three types of heavy holes in diamond-like semiconductors in nonquantizing magnetic fields

It is shown that when a diamond-like semiconducting crystal is placed in a nonquantizing magnetic fieldH [001], heavy holes are divided into three different groups according to their cyclotron trajectories and effective cyclotron masses.Ya. O. Galan Education Institute, Ternopol'. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 112–115, June, 1992.     

Auger recombination in diamond-like narrow-gap semiconductors

In the calculation of the transition rate of Auger recombination in the Kane model the overlap integral between the wave functions of the conduction and heavy hole bands is equal to zero at the threshold. As a result the preexponential function has a different temperature dependence in comparison with the case of simple parabolic bands. The theoretical value of the recombination lifetime is in agreement with experimental data for InSb at 300 K. Estimates of the overlap integral given earlier are analyzed.     

Exciton dispersion law in diamond-like semiconductors

It is shown that in covalent diamond-like semiconductors the minimum of the exciton energy is situated at non-zero exciton momentum if the heavy hole mass is large enough. The depth of the minimum may be of the order of the exciton binding energy. The minimal exciton energy is calculated for several semiconductors with the variational procedure.     

Long-lived excited impurity states in diamond-like semiconductors

The lifetime of charge carriers in the lowest excited states of some impurities of groups III and V in diamond, silicon, and germanium can be several (four to six) orders of magnitude longer that the lifetime of free carriers. Accumulation of carriers in these long-lived states may give rise to several new effects, such as hopping photoconductivity via long-lived excited states of impurities in dc and microwave electric fields, slow relaxation of induced absorption, and infrared absorption at energies lower than the impurity ionization energy. Zh. éksp. Teor. Fiz. 112, 221–236 (July 1997)     

Elastic magnetoimpurity resonance in diamond-like semiconductors (intravalley scattering)

The scattering by an excited neutral donor in Ge and Si near an energy-level crossing (on account of anisotropy of the effective mass) of the electronic states of the impurity as a function of the magnetic field is investigated. The crossing of the 2s-and 2p-like levels leads to the appearance of a nonzero dipole moment of the impurity atom and, therefore, a long-range potential, which is responsible for characteristic features in carrier transport. The transverse impurity conductivity is calculated. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 8, 549–554 (25 October 1996)     

Tunable fir lasers in semiconductors using hot holes

It is shown that active systems based on inter-subband transitions of hot holes could provide tunable FIR sources.Liquid helium cooled Ge is the most promising system—and some results are quoted—while for higher temperatures (with higher E and H fields) Si is the most likely material.     

Effective mass decrease due to electron-phonon interaction in heavy fermion systems

It is argued that in heavy fermion systems the electron-phonon interaction results in a decrease of the quasiparticle mass. This is in contrast to ordinary metals where this interaction is known to increase the effective mass. A simple expression is derived which relates the effective mass change to the electronic Grüneisen parameter, the Kondo temperature and the bulk modulus. For CeRu₂Si₂ the effective-mass decrease is estimated to be 25%.     

Photogeneration of electrons and holes in amorphous molecular semiconductors

This paper reports on the results of investigations into the photoconducting properties of amorphous molecular semiconductors based on films of two types: (i) poly(styrene) films doped with epoxypropylcarbazole (EPC) and a cationic polymethine dye (PD1) and (ii) poly(styrene) films doped with tetranitrofluorenone (TNF) and an anionic polymethine dye (PD2). Films of the first type possess p-type conductivity, whereas films of the second type exhibit n-type conductivity. It is found that, for films with n-type conductivity, unlike films with p-type conductivity, the activation energy of photogeneration of mobile charge carriers decreases with a decrease in the optical wavelength in the absorption range of the dyes. The possible mechanisms of the influence of the photoexcitation energy on the initial distance between charge carriers in electron-hole pairs are analyzed. The inference is made that, when the excess thermal energy of excited dye molecules dissipates at a low rate, the distance between the photogenerated electrons and photogeneration centers increases as compared to the distance between the photogenerated holes and photogeneration centers due to the electron-nucleus interaction.     

Effective electron-hole potential in polar semiconductors

Summary An accurate analytic expression for the electron-hole effective potential in polar semiconductors is derived, by use of a preceding self-consistent calculation of the author. Its form relies on the main assumption that the excitonic envelope function can be of the 1s-orbital form and that the ground-state wave function is well described in its phonon part by a coherent-state shape with a phonon displacement function depending on the relative electron-hole distance. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

The dielectric function of holes in semiconductors of zinc-blende structure

A closed analytic expression for the q and ω dependent dielectric function of the degenerate gas of holes in a zinc-blende or diamond structure semi-conductor is obtained in the random phase approximation (RPA). The limits of q → 0 and ω → 0 are examined and a comparison with previous developments is given. Significant deviations from the earlier results are found.     

To the theory of magnetic-moment anisotropy of shallow acceptor centers in diamond-like semiconductors

The spin quartet splitting of the ground state sublevels of shallow acceptor centers in a magnetic field has been calculated for diamond-like semiconductors with a strong spin-orbit coupling, such as Ge and GaAs. The anisotropy of this splitting has been shown to depend strongly on the binding energy and to be very sensitive to small changes in the Luttinger band parameters. These strong dependences permit one to use calculated ground-state g factors to determine the Luttinger magnetic band-structure parameters κ and q. A new method is proposed for determination of these parameters, and their values for Ge and GaAs are calculated.     

Effective interatomic potentials of liquid semiconductors

The effective interatomic potentials of liquid Te and Se have been derived from the observed structural data using the Born-Green equation. The effective interatomic potential of liquid Te has long range oscillation in real space as the same as in simple liquid metals but has a little difference for its oscillating phase near the region of the first and second nearest neighbour distances. While the effective interatomic potential of liquid Se has not shown the oscillating behaviour but is similar to that of molecular liquids like Ar.     

Effective Lagrangian for quantum black holes

We discuss the most general effective Lagrangian obtained from the assumption that the degrees of freedom to be quantized, in a black hole, are on the horizon. The effective Lagrangian depends only on the induced metric and the extrinsic curvature of the (fluctuating) horizon, and the possible operators can be arranged in an expansion in powers of M_P1/M, where M_P1 is the Planck mass and M the black hole mass. We perform a semiclassical expansion of the action with a formalism which preserves general covariance explicitly. Quantum fluctuations over the classical solutions are described by a single scalar field living in the (2 + 1)-dimensional world-volume swept by the horizon, with a given coupling to the background geometry. We discuss the resulting field theory and we compute the black hole entropy with our formalism.     

On the theory of laser sputtering through pairing of holes in compound semiconductors

A simple kinetic model is used to explain the observed dependence of the sputtering quantum yield on the laser fluence. The mechanism of sputtering presented here involves pairing of two holes against their repulsive Coulomb barrier, which depends on the concentration of photoexcited charge carriers through Debye screening. A threshold laser fluence is obtained at a concentration of photoexcited charge carriers that suppresses the barrier sufficiently to allow the pairing of holes at the surface bonds. The bonds are broken and atoms are ejected from the surface. The temperature dependence of the threshold laser fluence is discussed. Results agree qualitatively with experiments and existing theories.On leave of absence from: Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Lenin Boulevard, BG-1784 Sofia, Bulgaria     

Effective threshold energy for pair production in nonpolar semiconductors

A streaming model (high field) analysis is given for the average energy for and the probability of electron-hole pair production in a semiconductor when a quadratically energy dependent impact ionization cross-section exists above a threshold energy and competes with a nonpolar optical phonon scattering mechanism. A power series expansion method and tabulated results are provided to treat the resulting probability integrals of the form ∫₀^∞xⁿ exp {?(βx + x³)}dx.     

Effective masses of electrons and heavy holes in InAs,InSb, GaSb,GaAs and some of their ternary compounds

A survey is carried out for both electron and heavy-hole effective masses in InAs, InSb, GaAs, GaSb and some of their ternary compounds. Our computations are based on the pseudopotential method. To make allowance for the chemical disorder, the virtual crystal approximation is used, including a correction to the alloy potential. The agreement between our theoretical results and the experiment is very satisfying. A non-linearity dependence of the electron effective mass on the molar fraction has been shown for the ternary alloys under consideration, which indicates the alloying effect. This non-linearity disappears in the case of the heavy-hole effective mass for GaInSb.     

Polarization-dependent laser-induced giant mass transport in glassy semiconductors

Direct experimental evidence of the validity of the two-phase model of chalcogenide glass has been obtained. It has been shown that the polarization-light irradiation of glassy semiconductor films induces giant mass transport in the direction perpendicular to the polarization of the incident light. It has been revealed that a surface relief appears in the irradiated films. The shape of the relief depends on the laser polarization state. A macroscopic model qualitatively describing the observed phenomenon is presented.     

Effective two-dimensional description from critical phenomena in black holes

We study the occurrence of critical phenomena in four-dimensional, rotating and charged black holes, derive the critical exponents and show that they fulfill the scaling laws. Correlation function critical exponents and Renormalization Group considerations assign an effective (spatial) dimension,d=2, to the system. The two-dimensional Gaussian approximation to critical systems is shown to reproduce all the black hole's critical exponents. Higher order corrections (which are always relevant) are discussed. Identifying the two-dimensional surface with the event horizon and noting that generalization of scaling leads to conformal invariance and then to string theory, we arrive at 't Hooft's string interpretation of black holes. From this, a model for dealing with a coarse grained black hole quantization is proposed. We also give simple arguments that lead to a rough quantization of the black hole mass in units of the Planck mass, i.e.M(1/2)M _Pll with anl positive integer and then, from this result, to the proportionality between quantum entropy and area.This essay received the fifth award from the Gravity Research Foundation, 1994—Ed.     

Positive mass theorems for black holes

We extend Witten's proof of the positive mass theorem at spacelike infinity to show that the mass is positive for initial data on an asymptotically flat spatial hypersurface Σ which is regular outside an apparent horizonH. In addition, we prove that if a black hole has electromagnetic charge, then the mass is greater than the modulus of the charge. These results are also valid for the Bondi mass at null infinity. Finally, in the case of the Einstein equation with a negative cosmological constant, we show that a suitably defined mass is positive for data on an asymptotically anti-de Sitter surface Σ which is regular outside an apparent horizon.