Degenerate Valence Research Articles

Gallium arsenide photoluminescence under picosecond-laser-driven shock compression

A pump-and-probe technique was used to investigate shock effects on the photoluminescence spectra (∼833 nm) at T=80 K due to the direct transition E0 from the Γ6 conduction band to the Γ8 fourfold degenerate top valence band in GaAs. Under the shock loading condition, the photoluminescence peak was observed to blue shift and split into two components, corresponding to the transitions from the Γ6 conduction band to the valence heavy- and light-hole subbands, because of symmetry breaking by the uniaxial shock compression along the [001] direction. From the blue shift of the photoluminescence peaks, we deduced our picosecond-laser-driven shock pressure of ∼10 kbar.

Interband electronic Raman scattering of polarized light in cubic semiconductors with degenerate valence bands

The cross-sections are calculated for the Raman scattering processes with polarized light in cubic semiconductors whose valence band top is fourfold degenerate γ8. The exciton effect is taken into account.

Tunneling in k‐space. Application to degenerate valence band in the infinite spin–orbit interaction limit

AbstractHole tunneling between light and heavy mass bands in a homogeneous semiconductor due to a strong electric field is analyzed in the framework of spherical and at k = 0 degenerate bands when the spin–orbit interaction is infinite. Nonperturbative techniques are used to solve the problem. As in the case of zero spin–orbit interaction it is found that intervalence band tunneling takes place in a ring‐shaped volume whose symmetry axis is parallel to the electric field.

Free Carriers in Ionic Semiconductors with a Degenerate Valence Band Edge

physica status solidi (b)Volume 136, Issue 2 p. K119-K122 Short Note Free Carriers in Ionic Semiconductors with a Degenerate Valence Band Edge Yu. E. Perlin, Yu. E. Perlin V.I. Lenin State University, KishinevSearch for more papers by this authorSh. N. Gifeisman, Sh. N. Gifeisman V.I. Lenin State University, KishinevSearch for more papers by this authorV. P. Koropchanu, V. P. Koropchanu V.I. Lenin State University, KishinevSearch for more papers by this author Yu. E. Perlin, Yu. E. Perlin V.I. Lenin State University, KishinevSearch for more papers by this authorSh. N. Gifeisman, Sh. N. Gifeisman V.I. Lenin State University, KishinevSearch for more papers by this authorV. P. Koropchanu, V. P. Koropchanu V.I. Lenin State University, KishinevSearch for more papers by this author First published: 1 August 1986 https://doi.org/10.1002/pssb.2221360259Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume136, Issue21 August 1986Pages K119-K122 RelatedInformation

Tunnelling in k‐space application to degenerate valence bands

AbstractHole tunnelling between light and heavy mass bands in a homogeneous semiconductor due to strong electric fields is analyzed in the framework of the spherical and degenerate at k = 0 bands with spin‐orbit interaction neglected. It is found that in k‐space intense transitions between bands occur in a ring‐shaped volume, whose symmetry axis is parallel to the electric field. At high fields, of the order of 30 kV/cm, the average diameter of the ring, where hole tunnelling is most intense, becomes smaller than the diameter of the optical phonon sphere. As a result, before the collision with an optical phonon, the ballistically moving hole experiences velocity modulation. Some possible experimental situations which would allow to discriminate the hole tunnelling in the degenerate bands from the collision dominated processes, are discussed briefly.

Properties of two-dimensional hole gases of inversion and accumulation layers in magnetic fields

The Landau levels in inversion and accumulation layers at the interface between GaAs and p-type Al x Ga 1− x As are calculated self-consistently in the Hartree approximation. The degenerate valence band structure and the matching of the wave function at the interface are taken into account. The subband dispersion parallel to the interface has earlier been shown to be strongly non-parabolic and spin-split. This leads to a strongly non-linear B-dependence of the Landau levels. The inclusion of the magnetic field in the calculation is found to be crucial to get agreement with experimentally determined cyclotron effective masses. The calculated transition energies are partly in very good agreement with experiment. The dependence of the results on areal hole density, doping concentrations, valence band discontinuity etc. are also investigated.

AN INTEGRAL OPERATOR METHOD TO STUDY THE PROBLEM OF EXCITON-PHONON INTERACTION

In this article, taking the exciton and polar-phonon interaction as an example, we introduce an integral operator to deal with the dynamical problem of exciton-phonon interaction. Compared with the methods of earlier arthors, our method has some characteristics : besides the binding energies which agree with the measured data of experiments, the lifetime of excitons, the renormalization factors of translational masses, and the relation between these quantities and temperature, are obtained simultaneously. This method may be used not only for the Is state, but also the states higher than Is state. Furthermore, this method may be extended to the anisotropic case and the case of degenerate valence band conveniently.

Excitons in direct band gap cubic semiconductors

Perturbation is applied to study of the Wannier-Mott excitons in direct band gap cubic semiconductors with a fourfold degenerate highest valence band. The fine structure of exciton energy levels is investigated. General formulae are derived for the matrix elements of the perturbation. From these expressions it is straightforward to obtain values of the fine structure splittings of the energy levels and the wave functions of corresponding staes in any order of perturbation theory. A comparison with results of previous works is made.

Light-hole conduction in InGaAs/GaAs strained-layer superlattices

We report the first observation of light-hole band carriers in In0.2Ga0.8As/GaAs strained-layer superlattices by direct measurements of their effective mass (m*mo=0.14) using oscillatory magnetoresistance data. Preferential population of light-hole states, due to splitting of the degenerate bulk valence bands by built-in strain, allows this direct observation.

The quasienergy spectrum of semiconductors with direct band gaps in the laser field

Explicit analytical expressions are derived for Floquet states and the quasienergy spectrum of semiconductors with zinc-blende structure and direct band gaps, taking into account the real symmetry properties of the degenerate valence bands.

Ultraviolet two-photon spectroscopy of benzene: A new gerade Rydberg series and evidence for the 1 1E2g valence state

In the first application of continuously tunable ultraviolet two-photon absorption spectroscopy to a study of the higher excited states of a polyatomic molecule, we have obtained the two-photon absorption spectrum of jet-cooled benzene in the energy region from 55 000 to 75 000 cm−1. The strongest features of this spectrum, seen as two-photon resonance structure in three-photon ionization, are assigned to members of a new Rydberg series. Vibronic elements of these Rydberg states show evidence of dynamical effects associated with a Jahn–Teller instability in the 2E1g ionic core toward which the series converges. Notably, the magnitude of vibronic coupling terms in these states appears quite comparable to that present in C6H6+ and the sym-halobenzene cation ground states, while differing significantly from theoretical calculations predicting ν8 (ring stretch) as the major distorting mode. In addition, we observe two other new band systems: The first, with an origin at 60 800 cm−1, has vibronic structure, isotope shifts, and dramatically increased diffuseness upon deuteration, which taken together suggest its assignment as a highly valenized 3d Rydberg state or a degenerate valence state, most likely the lower of the two 1E2g states predicted by molecular orbital theory. The second, lying in the 55 000–58 000 cm−1 region, can be at least partially assigned to the two-photon forbidden 3px,y Rydberg states.

High-resolution resonant Brillouin scattering and the effect of stress on GaAs

Five-pass Fabry-Perot interferometry is used to obtain the linewidths of exciton polaritons resonant Brillouin scattered in GaAs. Both interbranch and intrabranch peaks are measured. An interpretation of the results in terms of excitons with an energy-independent damping is shown to be inadequate for GaAs. The effect of uniaxial stress is investigated and discussed. Stress-induced splitting (greater than the longitudinal-transverse splitting of the exciton) of the degenerate valence band at the $\ensuremath{\Gamma}$ point accounts for the observed decrease in the masses of the decoupled excitons. The values of these masses are in agreement with band-structure parameters. The value $\ensuremath{\delta}=0.0\ifmmode\pm\else\textpm\fi{}0.02$ meV for the exciton exchange parameter has been determined from these data.

The influence of the parallel magnetic field on the interband optical absorption in thin films

The effect of a parallel magnetic field on the interband optical absorption in size-quantized semiconductor layers is discussed on the basis of the effective mass approximation. The case of the simple and degenerate (germanium-like) valence band is considered.

Theory of transmission coefficients and resonant Brillouin scattering for three-branch exciton-polaritons

The three polariton branches connected with the heavy and light excitons in a semiconductor with a four-fold degenerate T8 valence band, such as GaAs, ZnSe and ZnTe, are considered. Calculation of electromagnetic reflection and transmission coefficients requires two additional boundary conditions. These are taken as homogeneous equations in the exciton fields and their derivatives at the boundary. Reflection and transmission coefficients for normally incident light are derived, and a condition for energy conservation is given in terms of those coefficients. The theory of resonant Brillouin scattering is given. It is assumed that coupling to the acoustic phonons occurs by means of the deformation potential, and the theory is given in a macroscopic linear response formulation. If interference terms can be neglected, the general form of the Stokes cross section reduces to a sum of nine lines, each of which has a skew form.

Electronic Raman Scattering of Polarized Light on Donor Levels in Semiconductors with Direct Band Gaps

AbstractExplicite approximate analytical expressions are derived for the differential cross sections of the electronic Raman scattering of circularly polarized light on donor levels with the electronic transition 1s → 2s in semiconductors with zincblende structure and direct band gaps. The photon energies are assumed to be nearly equal to the band gap and therefore the intermediate states in the valence bands give dominant contributions. The real symmetry properties of the degenerate valence bands are taken into account. The absolute values of the cross sections are calculated for GaAs.

Tetraquecksilbermethane, II [1]Tetrakis(halogenoquecksilber)-methane C(HgX)4 (X = F, Cl, Br und I): Synthesen und Schwingungsspektren / Tetramercurimethanes, II [1]Tetrakis(halomercuri)methanes C(HgX)4 (X = F, Cl, Br und I): Syntheses and Vibrational Spectra

Abstract The complete series of tetrakis(halomercuri)methanes C(HgX)4 (X = F, Cl, Br and I) was prepared by metathesis of tetrakis(acetoxymercuri)methane and aqueous hydrofluoric acid and solutions of halides (Cl-, Br-, and I-), respectively. All compounds are insoluble in most common solvents, but partly soluble in dimethylsulfoxide. Complete vibrational spectra indicate more or less ideally tetrahedral molecules C(HgX)4 in all cases. The originally triply degenerate valence vibrations of the CHg4 entities and the force constants for the C-Hg bonds show distinct correlations with the electronegativities of the halides X. On the other hand the totally symmetrical valence vibrations of CHg4 were found to be highly sensitive to variations in X, mainly due to coupling with the valence vibrations of the Hg-X-groups of the same symmetry species. Some analogies in the vibrational behaviour of the CHg4 fragments and of the isosteric NHg4 core in tetramercurioammonium complexes were observed and discussed.

Polariton effect in degenerate valence band semiconductors

We present a model which describes excitonic polariton effect for direct gap semiconductors where the valence band is degenerate, so that two (“light” and “heavy”) exciton dispersion curves exist and give rise to three polariton branches. It is shown that the quantity δ = Δ − 1 3 E LT is an important parameter in this case, Δ and E LT being respectively the exchange energy and the longitudinal transverse splitting. A comparison with the available data, extracted from Resonant Brillouin Scattering in GaAs, is carried out. It is shown that when only the uppermost and lowest polariton branches can be detected, the measured separation Δ exp between these two branches is equal to the longitudinal transverse splitting with a good approximation. In the general case the exact relation between Δ, E LT and Δ exp is derived.

Theory of electron-hole liquid in semiconductors

The random-phase approximation is generalized to include the effects of band anisotropy, coupling between degenerate valence bands, coupling to optical phonons, and the Hubbard exchange correction. This method is used to calculate the ground-state energy and equilibrium density of the electron-hole liquid in Ge, Si, AgBr, and various II-VI and III-V compounds and the thallous halides and lead chalcogenides. The results are compared to the experiments where they are available. Agreement is excellent for Ge and Si and reasonable for the other materials, considering the large uncertainties in the values of the band masses, etc. Substantial discrepancies remain between theory and experiment, however, in the cases of GaAs and ZnO.

Electrical properties of p‐Type GaAs

AbstractRelations for the effective drift mobility, the Hall coefficient, and the Hall mobility in p‐type group IV and III–V compounds are derived accounting for the degenerate valence band structure and acting scattering mechanisms. Improved deformation potentials are determined for holes in p‐type GaAs. Zn‐doped and Ge‐doped p‐type GaAs samples with hole concentrations in the range from 4 · 1017 to about 1020 cm−3 were analysed with regard to the temperature dependence of the Hall mobility, and it was found that the Brooks‐Herring formula is inadequate to describe ionized impurity scattering in p‐type GaAs.

Two‐Photon Absorption by Envelope–Hole Coupled Exciton States in Cubic ZnSe. II. Polarization Dependence in the Case of Degenerate Valence Bands

AbstractThe general angular dependence of two‐photon absorption for elliptical polarization is given in terms of complex polarization vectors in the case of cubic and spherical symmetry. The two‐photon transition probability for p‐like envelope–hole coupled exciton states is treated within an extended two‐band model which, for the case of degenerate valence bands, includes Hd‐term contributions of the exciton Hamiltonian. By use of the effective Bohr radii, resulting from the envelope–hole coupled exciton wave functions, the experimental polarization ratios yield good quantitative agreement with the values predicted theoretically.