Behavior of excitons and trions in CdTe/CdMgTe quantum-well structures with variations in temperature

The temperature-induced variations in the photoluminescence spectra measured in a magnetic field of trions and excitons in CdTe/CdMgTe quantum wells with modulated doping are studied. It is found that the temperature-induced redistribution of the intensity between the exciton and trion emission lines in a magnetic field is opposite to that expected from the simple Boltzmann distribution model. Coupled rate equations for the trion-exciton system are solved to construct the temperature dependences of the exciton and trion emission line intensities. The relations thus calculated are in good agreement with experiment.     

Resonance optical spectroscopy of long-period quantum-well structures

Theory of specular light reflection from long-period quantum-well structures taking into account the exciton contribution to dielectric polarization has been developed for an arbitrary relation between the background refractive index in the well, n _a, and barrier-material refractive index nb. General expressions for the optical reflection and transmission coefficients for a structure with N equidistant quantum wells are derived with the use of the Green’s function and transfer matrix methods. Normal and oblique light reflectance spectra from II-VI-based heterostructures were found to reveal a bright interference pattern caused by the difference between n _a and n _b. A comparison of the theory with experiment has yielded the dispersion of n _a and n _b within a broad wavelength range and the parameters of the quasi-two-dimensional heavyhole exciton (e1-hh1), namely, the resonant frequency and the radiative and nonradiative damping rates. Reflectance spectra from resonant Bragg and quasi-Bragg structures with real exciton parameters are calculated, and the effect on these spectra of the refractive-index difference and the deviation from the Bragg condition is analyzed. Fiz. Tverd. Tela (St. Petersburg) 39, 2072–2078 (November 1997)     

Photoluminescence of ZnMnTe quantum-well structures in a magnetic field

Photoluminescence spectra of strained structures Zn_{1 ? x} Mn _x Te/Zn_{1 ? y} Mg _y Te with magnetic quantum wells and nonmagnetic barriers are studied. The Zeeman splitting of the heavy exciton is found to follow an unusual behavior: both spin components shift down in energy. The heavy-exciton photoluminescence Zeeman components are observed to be inversely distributed in intensity, with the higher energy component being stronger than the lower energy component. The Zeeman splitting of the exciton in a magnetic field is calculated. The data obtained permit refinement of some parameters of the energy spectrum and magnetic properties of these structures.     

Nonreciprocal Optical and Magnetooptical Effects in Semiconductor Quantum Wells

Physics of the Solid State - Abstract—Effects implying violation of the Fresnel light reflection laws in semiconductor structures with quantum wells (QWs) have been investigated. This...     

Photoluminescence of single quantum wires and quantum dots

The results of a study into the photoluminescence spectra of a set of quantum dots based on GaAs enclosed in AlGaAs nanowires are presented. The steady state and time resolved spectra of photoluminescence under optical excitation both from an array of quantum wires/dots and a single quantum wire/dot have been measured. In the photoluminescence spectra of single quantum dots, emission lines of excitons, biexcitons and tritons have been found. The binding energy of the biexciton in the studied structures was deduced to be 8 meV.     

Effect of substrate misorientation on quantum-dot size distribution in the InAs/GaAs system

A study is reported of the effect of (001)GaAs substrate misorientation in the [010] direction on the distribution of MBE-grown self-assembled InAs/GaAs quantum dots in size and position in the GaAs matrix. Temperature-induced narrowing of the exciton photoluminescence line of a quantum-dot ensemble caused by redistribution of photoexcited carriers among dots of different size has been observed. Fiz. Tverd. Tela (St. Petersburg) 40, 855–857 (May 1998)     

Trions in quantum-well structures with two-dimensional electron gas

A study has been made of bound exciton-electron complexes (trions) and unbound exciton-electron states (combined exciton-cyclotron resonance) from reflectance spectra obtained from modulation-doped CdTe/CdMgTe quantum-well structures. It has been established that the contribution of trions to dielectric permittivity is comparable to that of excitons. An analysis is made of the magnetic-field dependence of the parameters describing the contribution to dielectric permittivity due to exciton-cyclotron-resonance states. Fiz. Tverd. Tela (St. Petersburg) 40, 813–815 (May 1998)     

Optical studies of ZnSe/ZnMgSSe-based quantum-well semiconductor heterostructures

Results of an optical study of heterostructures based on new compounds, ZnSe/ZnMgSSe, are presented. The possibility of using these compounds to produce high-quality quantum-well structures having strong exciton features in optical spectra is demonstrated. An analysis of reflectance spectra has yielded the exciton parameters: the resonant frequency, oscillator strength, and exciton line damping. The exciton binding energies have been determined from magneto-optical spectra. The samples studied have a high structural perfection and small inhomogeneous width of the excitonic resonances. Fiz. Tverd. Tela (St. Petersburg) 40, 811–812 (May 1998)     

Magnetic-field-effects on photoluminescence polarization in type II GaAs/AlAs superlattices

Optical orientation and alignment in the presence of a magnetic field have been applied to study the fine structure of excitons in type II GaAs/AlAs superlattices. We have developed a theory of polarized photoluminescence taking into account the anisotropic exchange splitting of the radiative excitonic doublet. The observed effects of the longitudinal and transverse magnetic fields on the polarization of the exciton emission unambiguously confirm that the actual symmetry of the exciton is lower that D_2d and that there exist two classes of excitons with opposite signs of the anisotropic exchange splitting.