arXiv subjects
Publications and source records attributed to D. A. Contreras-Solorio.
The "one-dimensional" coherent states are applied to describe the Shubnikov - de Haas and the de Haas-van Alphen oscillation effects in metals, semimetals, and degenerate semiconductors. The oscillatory part of the electron density of states in a magnetic field is calculated. A substantial simplification of calculations is achieved.
The reflection, transmission and absorption of a symmetric electromagnetic pulse, which carrying frequency is close to the frequency of an interband transition in a QW (QW), are obtained. The energy levels of a QW are assumed discrete, one exited level is taken into account. The case of a wide QW is considered when a length of the pulse wave, appropriate to the carrying frequency, is comparable to the QW's width. In figures the time dependencies of the dimensionless reflection, absorption are transmission are represented. It is shown, that the spatial dispersion and a distinction in refraction indexes influence stronger reflection.
The non-sinusoidal character oscillations appear in the transmitted, reflected and absorbed light fluxes when light pulses irradiate a semiconductor quantum well (QW), containing a large number of the equidistant energy levels of electronic excitations. A damping echo of the exciting pulse appears through the time intervals $2π\hbar/ΔE$ in the case of the very short light pulses $γ_l^{-1}\ll\hbar/ΔE$.
A theory of light transmission through a quantum well (QW) in a magnetic field perpendicular to the QW plane is developed. The light wave length is supposed comparable with the QW width. The formulas for reflection, absorption and transmission take into account the spatial dispersion of the light monochromatic wave and a difference of the refraction indexes of the QW and barrier. We suppose a normal light incidence on the QW plane and consider only one excited energy level. These two factors influence mostly light reflection, since an additional reflection from the QW borders appears to the reflection due to interband transitions in the QW. The most radical changes in reflection appear when a radiative broadening of the excited energy level is small in comparison to a nonradiative broadening. Our theory is limited by the condition of existence of size-quantized energy levels which is satisfied for quite narrow QW's.
It has been shown that the non-sinusoidal character oscillations appear in the transmitted, reflected and absorbed light fluxes when light pulses irradiate a semiconductor quantum well (QW), containing a set of a large number of the equidistant energy levels of electronic excitations. The oscillation amplitude is comparable to the flux values for the short pulses, duration of which γ_l^{-1} \leq \hbar/ΔE. A damping echo of the exciting pulse appears through the time intervals 2π\hbar/ΔE in the case of the very short light pulses γ_l^{-1}\ll \hbar/ΔE. Symmetrical and asymmetrical pulses with a sharp front have been considered. Our theory is applicable for the narrow QWs in a strong magnetic field, when the equidistant energy levels correspond to the electron-hole pairs with different Landau quantum numbers.
The light absorption {\cal A} and reflection{\calR} coefficients for a three-level system in a quantum well (QW) in a strong magnetic field {\bf H}, directed perpendicularly to the QW's plane, have been calculated. The energy levels correspond to the ground state and to magnetopolaron energy levels \hbarω_{1(2)} with the inverse lifetimes γ_{r1(2)} and γ_{1(2)}. The inverse radiative lifetime of an EHP in a QW γ_{rξ}(\bf{\cal K}_{\perp})\not=0 only under condition {\cal K}_{\perp}\leω_ξn/c, where \hbarω_ξis the EHP energy. It has been shown that γ_{rξ}(\bf{\cal K}_{\perp}) is proportional to H. The values γ_{ra}(\bf{\cal K}_{\perp}) and γ_{rb}(\bf{\cal K}_{\perp}) for an excitation consisting of a hole and a usual magnetopolaron have been calculated. The index a(b) designates a magnetopolaron upper (lower) term. In the resonance at H_{res}=m_ecω_{LO}/|e|~~ γ_{ra}^{res}=γ_{rb}^{res}=γ_{rξ_0}^{res}/2, where the index ξ_0 corresponds to the EHP with n_e=n_h=1. The dependencies {\cal A}(H)$ and ${\cal R}(H) for various values of ω_l in the magnetophonon resonance vicinity have been obtained. The existence of "combined"and "weak" polarons has been predicted. The resonant value H_{res} for the combined polaron case depends on a QW's depth and width.
The method of detection and investigation of the magnetopolaron effect in the semiconductor quantum wells (QW) in a strong magnetic field, based on pulse light irradiation and measuring the reflected and transmitted pulses, has been proposed. It has been shown that a beating amplitude on the frequencies, corresponding to the magnetopolaron energy level splitting, depends strongly from the exciting pulse width. The existence of the time points of the total reflection and total transparency has been predicted. The high orders of the perturbation theory on electron-electromagnetic field interaction have been taken into account.
In the present study we calculate the energy values and the spatial distributions of the bound electronic states in some diffused quantum wells. The calculations are performed within the virtual crystal approximation, $sp^3 s^*$ spin dependent empirical tight-binding model and the surface Green function matching method. A good agreement is found between our results and experimental data obtained for AlGaAs/GaAs quantum wells with thermally induced changes in the profile at the interfaces. Our calculations show that for diffusion lengths $L_{D}=20\div100$ Å the transition (C3-HH3) is not sensitive to the diffusion length, but the transitions (C1-HH1), (C1-LH1), (C2-HH2) and (C2-LH2) display large "blue shifts" as L_{D} increases. For diffusion lengths $L_{D}=0\div20$ Å the transitions (C1-HH1) and (C1-LH1) are less sensitive to the L_{D} changes than the (C3-HH3) transition. The observed dependence is explained in terms of the bound states spatial distributions.
We study long-wavelength polar optical modes at semiconductor interfaces of GaAs|Al_{(x)}Ga_{(1-x)}As and take into account influence of the Al concentration. We have considered two cases in which the interface is kept at unfixed and fixed electrostatic potential. The spectrum of excitation then shows existence of localized and resonant modes to depend on the concentration of Al. For the case of a fixed electrostatic potential, a splitting of the resonant mode near the transverse threshold is found for certain ranges of the concentration x. The existence of these modes has been obtained by computing the spectral strength through the Surface Green Function Matching (SGFM) method.