Yu. I. Mazur

Carrier transfer in self-assembled coupled InAs/GaAs quantum dots

Photoluminescence (PL) spectra and time-resolved PL data from AlGaAs/GaAs superlattice structures containing thin InAs layers of about 1–3 monolayer grown on semi-insulating (001)-oriented GaAs substrates at lowered temperatures are studied. The size distribution of InAs quantum dots (QDs) among different families (modes) is controlled by variation of growth temperature and/or growth interruption. We demonstrate the stabilization of the PL magnitude caused by strong coupling between different modes and the full width at half maximum of “large size” QD modes within a certain temperature interval (50–150 K) due to feeding of the radiative transitions from nonradiative decay and carrier transfer arising from decaying excitonic states of the small size QD modes. Strong competition between different channels of ground state relaxation leads to an oscillating dependence of the PL transient for the small size QD mode. Efficient inter- and intramode tunneling rules out “bottleneck restrictions” for the PL. The pa...

Far-infrared reflectivity study of lattice dynamics of narrow-gap HgCdMnTe semiconductors

We report the results of a comprehensive study of lattice dynamics by means of far-infrared phonon spectroscopy in quaternary semimagnetic narrow-gap single crystals. A new version of the isodisplacement model is developed which takes into account the peculiarities of the dielectric function of narrow-gap semiconductors. This new approach is used to describe the phonon spectra transformation with composition for quaternary materials and is found to be in excellent agreement with the experimental data. The evidence for better quality and more stabilized crystalline structure of in comparison with ternary is presented and ascribed to the effect of magnetic doping.

Thickness dependence of disorder in pseudomorphic modulation-doped AlxGa1-xAs/InyGa1-yAs/GaAs heterostructures

The dependence of disorder on InyGa1-yAs thickness in pseudomorphic strained-layer AlxGa1-xAs/InyGa1-yAs/GaAs heterostructures is studied by means of photoluminescence (PL) and Raman scattering. PL and Raman data indicate that, for both y = 0.10 and 0.15, the InyGa1-yAs layers (with thickness not greater than 20xa0nm) are purely pseudomorphically strained. For InyGa1-yAs wells narrower than about 15xa0nm, the broad PL emission, small correlation length derived from Raman measurements of the longitudinal optical (LO) phonons, the asymmetry of the LO phonon peak and the presence of a disorder-activated longitudinal acoustic (DALA) phonon signal in the Raman scattering data are all indicative of disordered InGaAs. For well widths of 20xa0nm, however, the narrow PL emission, the details of the LO phonon data and the absence of an observable DALA signal are all indicative of much less disorder than in the thinner quantum wells.

Excitonic magnetoluminescence enhancement in semimagnetic

Quaternary (x = 0.31 - 0.38, y = 0.008 - 0.02) crystals grown by the travelling heater method were investigated by means of magnetoluminescence over a wide temperature (5 K < T < 100 K) and magnetic field range. The observed non-monotonic evolution of the photoluminescence spectra with temperature and magnetic field is interpreted in terms of exciton localization in alloy fluctuations and exchange interaction between the free carriers and the localized spins of the 3d electrons in the magnetic ions. From that new arguments are drawn with respect to a structural improvement of ternary by doping with manganese ions.

Photoluminescence excitation due to hot excitons in narrow-gap

We present new results on infrared photoluminescence and photoluminescence excitation spectroscopy in . We find that the phonon coupling significantly influences the optical spectra of this direct narrow-gap semiconductor. In a small spectral region close to the fundamental energy gap, indirect `hot exciton absorption with participation of longitudinal optical phonons is the main absorption mechanism. A qualitative theoretical explanation is given. Furthermore, new experimental arguments for the excitonic nature of the optical transitions in the spectral region of the fundamental gap in this narrow-gap material are provided. We find that knowledge about the excitonic processes in wide-gap semiconductors can also be applied to high-quality narrow-gap materials.

Peculiarities of interband photoluminescence in the semimagnetic semiconductor Hg1−xMnx Te

Abstract The results of photoluminescence (PL) investigations of semimagnetic Hg 1− x Mn x Te single crystals are presented. The crystal composition range ( x = 0.104, 0.167, 0.202) demonstrates the transformation of photoluminescence spectrum when the effective g -factor changes its sign. Temperature and magnetic field dependencies have shown a strong non-monotonic behaviour of edge emission feature. An extremely narrow half width (2.5 meV) is observed at B = 2.3 T for x = 0.104. The blue shift of photoluminescence maximum with increasing magnetic field is described by the modified Pidgeon-Brown model. For x = 0.167 and x = 0.202 a strong asymmetry of the photoluminescence peak is detected. Its behaviour in a magnetic field requires further corrections in the Pidgeon-Brown consideration. Some arguments for a magneto-polaron mechanism of PL temperature dependencies are presented.

Peculiarities of the exchange interaction in narrow-gap Hg1-x-yCdxMnySe

The peculiarities of the exchange interaction between the carrier spin and localized spin moments of magnetic ions near the semimetal-semiconductor transition have been studied in a semimagnetic quaternary solid solution system, Hg1-x-yCdxMnySe (x = 0.10, y = 0.02, Eg = 45 meV), by means of Shubnikov-de Haas oscillations. The measurements show that the exchange `constant is actually a somewhat complicated function of energy gap Eg and electron concentration, which changes from negative values ( N0 = -0.15 eV) at lower electron concentration to positive values ( N0 = 0.28 eV) at higher electron concentration, values which are more typically associated with wide-gap semimagnetic semiconductors.

Magnetic field enhanced luminescence in diluted narrow gap Hg1-xMnxTe

Peculiarities of photoluminescence manifestation in narrow-gap Hg 1-x Mn x Te (0.09 < x < 0.11) under variation of both the magnetic field (0-7 T) and temperature (4-130 K) have been studied. A strong resonance enhancement of the edge emission and a narrowing of the linewidth to less than 2.5 meV were detected. The model of a magnetically trapped exciton fits well the photoluminescence behaviour observed. The magnetic field and temperature effects in photoluminescence are consistent with the suggested model.