Size-quantized Semiconductor Film Research Articles

Thermoelectric transport properties of semiconductor film-based epitaxial monolayer graphene

ABSTRACT Epitaxial graphene on semiconductor films has potential for various applications due to its thermoelectric properties. We investigated factors affecting its thermo power using a solid-state physics approach, considering the interaction between the substrate and graphene, and exploring the effects of chemical potential, temperature, anharmonic vibrations of atoms, phonon-drag, and film thickness. Our results show that anharmonic effects significantly enhance the thermopower caused by electrons, especially at higher temperatures. Additionally, we observed an increase in total thermopower due to phonon-drag, although it has negligible effects at or above room temperature. We found that the thermopower on size-quantized semiconductor films is significantly higher than on metal conductor films and bulk semiconductor substrates. Decreasing the film thickness further increases the thermo power, providing an effective way to enhance the thermo electric properties of epitaxial graphene. Our findings contribute to a better understanding of the thermoelectric properties of epitaxial graphene on semiconductor films and offer valuable insights for future applications.

Effects of Nonparabolicity on Electron Thermopower of Size-Quantized Semiconductor Films

Effects of nonparabolicity of energy band on thermopower, in-plane effective mass and Fermi energy are investigated in size-quantized semiconductor films in a strong while non-quantized magnetic field. We obtain the expressions of these quantities as functions of thickness, concentration and nonparabolicity parameter. The influence of nonparabolicity is studied for degenerate and non-degenerate electron gases, and it is shown that nonparabolicity changes the character of thickness and the concentration dependence of thermopower, in-plane effective mass and Fermi energy. Moreover, the magnitudes of these quantities significantly increase with respect to the nonparabolicity parameter in the case of strong nonparabolicity in nano-films. The concentration dependence is also studied, and it is shown that thermopower increases when the concentration decreases. These results are in agreement with the experimental data.

Absorption coefficient of size-quantized A3B5 semiconductor film with dislocations

The indirect absorption of light by size-quantized semiconductor film is theoretically investigated. It is supposed that the mechanism of indirect absorption is conditioned by charge carrier's scattering on dislocations. The dispersion law of electron in the immediate vicinity of the maximum of valence band is considered as non-parabolic and is described in two-band Kane approximation. The absorption coefficient is calculated. It is shown, that under non-parabolic dispersion law of electron the dependence of absorption coefficient on (ℏω-εv(0)) near the absorption edge has quadratic dependence. It is shown, that the non-parabolicity of dispersion law results in increased absorption coefficient.

Indirect transitions in thin films due to the coulomb interactions between electrons

The absorption coefficient in the indirect transitions due to the Coulomb interactions between electrons in thin size-quantized semiconductor film has been calculated. The calculation has been carried out for the case of high density of electrons and small transfer of momentum ℏ q → , when the light absorption is connected with emission of plasmons. The frequency dependence as well as dependence on the concentration of conductivity electrons and thickness of the film has been obtained.

Electric field effect on exciton absorption in size-quantized semiconductor film

Effect of an uniform electric field on optical absorption in a quantized semiconductor film, far off an exciton resonance, is theoretically investigated. To the quasi-classical approximation, the expression is obtained for an exciton factor in the coefficient of an interband absorption, and the ionization probability of a 2D exciton in the presence of an external electric field is calculated.

Indirect transitions caused by electron—dislocation interaction in size-quantized semiconductor film

The light absorbtion coefficient of a semiconductor film caused by indirect electronic transitions is calculated under the assumption that the part of the third body plays a dislocation. There is obtained the frequency dependence of the absorbtion coefficient at various orientations of dislocations in the film. The comparison is carried out of the suggested mechanism with known mechanisms of indirect transititions.

Interband Raman scattering in size-quantized semiconductor films

The interband Raman scattering in size-quantized semiconductor films is studied theoretically. The process involves an interband electronic transition and an intraband transition between subbands. Calculations show that the spectrum of the scattered radiation exhibits striking resonances for frequencies equal to the frequencies of the intersubband transitions. The magnitude of the scattering efficiency associated with the resonance suggests that it may be possible to use interband Raman scattering to measure the energy spectrum of size-quantized semiconductor films.

The influence of the parallel magnetic field on the inter-subband optical absorption in thin films

The influence of the magnetic field parallel to the surface of the size-quantized semiconductor film on the energy spectrum, and on the inter-subband optical absorption is discussed in terms of the effective mass approximation. The effect of the spin-orbit interaction is taken into account. The frequency-dependent conductivity is calculated.

On the optical transitions in size quantized films

The effect of the gauge choice on the boundary conditions proposed by Valkov and Pinsker, and on optical transitions in size quantized semiconductor films, is discussed.

On the optical transitions in size quantized films

The effect of the gauge choice on the boundary conditions proposed by Valkov and Pinsker, and on optical transitions in size quantized semiconductor films, is discussed.

Two-photon absorption in size-quantized films with tilted valleys

Abstract Two-photon interband transitions in a size-quantized semiconductor film with tilted energy ellipsoids (relative to the surface layer) are discussed in terms of the effective mass approximation. An explicit expression for the two-photon transition rate is derived for the radiation field of arbitrary polarization. The transition rate is calculated numerically for the (001) PbTe film.

Two-photon interband absorption in size-quantized semiconductor films

The two-photon interband transition probability in a semiconductor film is discussed taking quantum size effects into account. An explicit expression for the transition rate is derived for arbitrary polarization of light with respect to the surface normal. The feasibility of studying the discrete energy levels of electrons in a thin film by means of two-photon spectroscopy is shown.