Energy Spectrum Of Holes Research Articles

Intersubband optical absorption of holes in quantum wells

The problem of hole energy spectrum and interlevel optical absorption in p -type quantum wells is considered theoretically. To obtain analytical results, terms in the Luttinger Hamiltonian containing in-plane momentum are treated as a perturbation. In this approximation energy spectrum, wave functions, hole statistics and interlevel optical matrix elements can be found for an arbitrary shape of quantum well. Finally, optical absorption spectra are calculated for different interlevel transitions.

Optical investigation of the two-dimensional hole energy spectrum in GaAs/AlxGa1−xAs heterojunctions

We present the results of optical studies on the energy spectrum of a two-dimensional hole gas (2DHG) in a GaAs/AlxGa1−xAs structure. The photoluminescence (PL) line shape in the 2DHG is investigated as a function of temperature by heating the holes by a current flow through the 2D hole channel. The line shape of the PL from the 2DHG as a function of temperature is calculated by taking into account the real band structure and the hole–hole final-state interaction. By comparing experiment and theory, it is found that the special features of the band structure predicted theoretically explain the experimental data.

Luminescence polarization of CdSe microcrystals with hexagonal lattice structure

We have considered theoretically the luminescence polarization of small CdSe microcrystals due to the hexagonal structure of the lattice. We derive the energy spectrum and wave functions of holes in spherical microcrystals. It is shown that the value of the splitting between the A and B hole states in microcrystals could be five times smaller than the corresponding value of crystal-field splitting Δ in bulk hexagonal semiconductors. The polarization of light connected with transitions between the electron and hole quantum size levels were calculated. It is shown that nonequilibrium electron-hole pairs, with long lifetimes, are formed in microcrystals as a result of the hole thermalization to the A state after excitation into the B state. The recombination of these states requires the participation of phonons, resulting in a strong dependence of the recombination rate on the temperature. The time dependence of the luminescence polarization is found.

Absorption and intensity-dependent photoluminescence measurements on CdSe quantum dots: assignment of the first electronic transitions

CdSe is used as a prototype to show the implications of valence-band degeneracy for the optical properties of strongly quantum-confined nanocrystals. Absorption spectra and photoluminescence spectra obtained under intermediate and strong pulsed excitation show the presence of new structures. The energy levels for the electron and the hole are calculated with the spherical confinement, the nonparabolicity of the conduction band, and the valence band degeneracy taken into account. The oscillator strengths of the dipole-allowed transitions are also calculated. This model is found to be in good agreement with the experimental observations, which originate mainly from the quantization of the energy spectrum of holes with due account given to valence-band degeneracy.

Luminescence polarization of CdSe microcrystals.

We have considered theoretically the polarization of the luminescence of small CdSe microcrystals due to the hexagonal structure of the lattice. We derive the energy spectrum and wave functions of holes in spherical microcrystals. It is shown that the value of the splitting between the A and B hole states in microcrystals could be five times smaller than the corresponding value of crystal-field splitting \ensuremath{\Delta} in bulk hexagonal semiconductors. The times of radiative recombination and the polarization of light connected with transitions between the electron and hole quantum size levels (QSL's) were calculated. The time dependence of the luminescence polarization has been found. At the first instant after short impulse excitation the degree of polarization should be equal to 13/51. It is shown that nonequilibrium electron-hole pairs, with long lifetimes, are formed in microcrystals as a result of the hole thermalization to the A state after excitation into the B state. The recombination of these states requires the participation of phonons, resulting in a strong dependence of the recombination rate on the temperature. The degree of luminescence polarization of these states depends on the type of phonons involved in optical transitions.

Optical properties of semiconductor nanocrystals with degenerate valence band

The energy spectrum and wave functions of holes in CdSe and CdS nanocrystals have been calculated. It is shown that in CdS nanocrystals the lowest quantum size level (QSL) of holes has p-type symmetry and optical transitions between this state and the lowest QSL of electrons are forbidden. The radiative lifetimes in CdSe nanocrystals are estimated to be of the order of 23 ns. The real structure of the valence bands have been shown to increase the electron-hole pair — polar phonons coupling with decreasing nanocrystal size.

Energy-band structure for strained p-type Si1-xGex.

Results of the valence-band structure in strained ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ge}}_{\mathit{x}}$ are given as a function of the germanium content, x. The interactions between the ${\mathit{p}}_{3/2}$ and ${\mathit{p}}_{1/2}$ bands are taken into account by using a 6\ifmmode\times\else\texttimes\fi{}6 Hamiltonian in the form of the ${\mathit{JM}}_{\mathit{J}}$ representation. The Hamiltonian is given in two parts, viz., the unstrained Hamiltonian of Dresselhaus, Kip, and Kittel, and the strained Hamiltonian of Kleiner and Roth. With this 6\ifmmode\times\else\texttimes\fi{}6 Hamiltonian, the hole-energy spectrum for the two ${\mathit{p}}_{3/2}$ bands and the ${\mathit{p}}_{1/2}$ band is obtained; knowledge of which is crucial for determining pertinent electronic-transport data.

Acoustoelectric current quantum oscillations in LiNbO 3-BiSb layered structure

Acoustoelectric current giant quantum oscillations have been measured in LiNbO 3-Bi 0.99Sb 0.01 layered structure at H ⩽ 40 kOe and T = 4.2 K along bisectornal C 1 and binary C 2 sample crystallographic axes. Obtained data allows us to estimate the Fermi surface effective cross-section areas. Proposed method is useful for electron and hole energy spectrum investigations in semimetals.

Generation of far-infrared radiation by hot holes in germanium and silicon inE ?H fields

The experimental results obtained by the investigation of stimulated FIR emission from dopedp-type germanium andp-type silicon by hot holes in crossedE andH fields atТ = 10 and 80 K are reported. The analysis of the emission intensity fromp-type germanium as a function ofE andH fields permits us to draw a conclusion about the important role of quantization of the energy spectrum of light holes and the contribution of light hole transitions with Δn = 2 to the amplification of FIR radiation. A new region of generation is demonstrated inp-type germanium under uniaxial stress. The first experimental results on stimulated FIR emission fromp-type silicon are reported.

The band structure of strong-correlated electrons in La 2− xSr xCuO 4 and YBa 2Cu 3O 7− y

In the tight-binding scheme the band structure of La 2− x Sr x CuO 4 and YBa 2Cu 3O 7− y is calculated with taking into consideration strong correlations. The insulator gap and density of states near band edgeare shown to be similar in La 2CuO 4 and YBa 2Cu 3O 6. All bands of holes are narrow: the higher the energy the narrower the band. In YBa 2Cu 3O 6.5+ x 1D-band formed by Cu-O chains is inside the 2D-gap of CuO 2-planes. When x ⪌ 1 the energy spectra of holes in La 2− x Sr x CuO 4 and YBa 2Cu 3O 6.5+ x are similar. At x = x c = 0.2 + 0.3 electronic structure transformation takes place; at x > x c 1D-states are overlapping with 2D-states in the vicinity of the Fermi level.

Electronic specific heat and magnetic susceptibility in bismuth thin films under three-dimensional quantization.

Three-dimensional quantization of the energy spectrum of electrons or holes can be realized in semimetal bismuth by applying a magnetic field perpendicular to the bismuth thin film. Numerical calculations were made of the energy (of the charge carriers), electronic specific heat, electronic magnetization, and magnetic susceptibility in three-dimensionally quantized bismuth films. The nonparabolic, ellipsoidal electronic band model for bismuth was used and the films were perpendicular to the trigonal axis. The aforementioned thermodynamical quantities were systematically evaluated as functions of temperature, film thickness, and magnetic field intensity.

Molecular interpretation and prediction of the dynamic viscoelastic properties of crosslinked polymers

The dynamic viscoelastic properties of epoxy resins through the glass transition region are theoretically calculated and molecularly interpreted. Good agreement between the theoretical and experimental results is achieved over a broad range of temperatures and frequencies with a single set of molecular parameters. All molecular parameters are independent of temperature and frequency and can be determined separately. The master dynamic storage modulus and loss tangent are uniquely defined by a single parameter that characterizes the shape of the hole energy spectrum. The transition from a Williams-Landel-Ferry (WLF) (or Doolittle) dependence to an Arrhenius temperature dependence of the relaxation timescale (shift factor) in the vicinity of T g is predicted and interpreted in molecular terms. The dynamic response of crosslinked polymers is quite similar to that of amorphous polymers. However, the timescale and the hole energy spectrum are orders of magnitude longer and broader, respectively. As a result, we have found higher activation energy, more frozen-in free volume and smaller effect of physical ageing on the dynamic properties of crosslinked systems.

Glass transition and relaxation: A new free volume model

We describe the glass relaxation in terms of the collapse of a series of free volume having different creation energies but having equal volume. The equation of state and the non-equilibrium equations are derived. The general solution of the new molecular kinetic equations is obtained and the relaxation function is found to have the form of a “Kohlrausch-Williams-Watts” function. If the relaxation time were structural independent, the relaxation function should have the classical Debye exponential form. As temperature is decreased, the width of the hole energy spectrum increases due to the increase of the shift factor.

Plasma reflection and hole optical effective mass in p‐HgTe

AbstractThe results of plasma reflection investigations in p‐HgTe are described. It is shown, that the plasma reflection spectrum shift towards small energies and the decrease of their depths with increasing temperature cannot be explained by the dielectric anomaly of the zero gap semiconductor due to the Γ8 → Γ8 transition only. The analysis of the experimental results shows that the optical effective mass value has both, a temperature and concentration dependence. Such a dependence may be explained in the frame of the Kane theory, if the renormalization of the energy spectrum of holes due to exchange electron—electron interaction is taken into account.

Energy spectrum and optical absorption in p-CdGeAs2

In the Kein four-band model, taking account of interaction with excited bands, the energy spectrum and effective masses of electrons and holes in CdGeAs2 are calculated. The polarizational dependence of the optical absorption spectrum is investigated for transitions between bands of light and heavy holes. The results are compared with experimental data.

Theory of mean removal energies for single particles in nuclei

A useful way to characterize the hole-energy spectrum excited in a direct particle-removal reaction like ($p,2p$) or ($e,{e}^{\ensuremath{'}}p$) is through the centroid or mean removal energy. We derive the rules for computing this quantity in a linked-cluster expansion, and give some examples. We demonstrate the close relation of the mean removal energy to Brandow's self-consistent orbital energy, and discuss briefly the connection with Green's function theory.[NUCLEAR STRUCTURE Linked-cluster theory of mean or centroid removal energies measured in ($p,2p$) or ($e,{e}^{\ensuremath{'}}p$); applications and relation to other hole energies.]

Intraband Magnetic Breakdown in Tellurium

AbstractThe investigation of the Shubnikov‐de Haas effect in tellurium revealed some unusual phenomena which can be explained by an intraband magnetic breakdown of hole trajectories in k‐space close to the saddle‐point of the hole energy spectrum. These features of the magnetoresistance behaviour including, for example, the occurrence of the zeroth oscillation maximum in a magnetic field perpendicular to the trigonal axis in the case of an energy band with completely lifted spin degeneracy, are in satisfactory quantitative agreement with the existing theory of intraband magnetic breakdown.