N.B. Brandt

Method for elastic uniaxial stress of single crystals: description and applications

The original method for a strong elastic uniaxial compression of single crystals up to 5 ÷ 6 kbar, calibration procedure and its applications for semimetal and semiconductor samples are described in details for the first time. This method simplifies sample installation and adjustment; it prevents the frequent destruction of samples, which often takes place in conventional methods of uniaxial compression between two anvils.

The emission spectrum of p-AlGaAs/GaAsP/n-AlGaAs diodes under uniaxial compression

AbstractNew experimental data are presented on the effects of uniaxial compression of up to 4 kbar along the [110] and [1

Size quatized levels of the valence band and the optical gain in strained p-AlGaAs/GaAsP/n-AlGaAs structures under uniaxial compression

nbar 1n

Peculiarities of the electron transport in very short period InAs/GaAs superlattices near quantum dot formation

0] crystallographic directions on the spectra of electroluminescence and the current-voltage characteristics of diodes based on n-AlxGa1 − xAs/GaAsyP1 − y/p-AlxGa1 − xAs (y = 0.84) heterostructures that were designed for injection lasers. With increasing pressure, the spectra show a shift to shorter wavelengths, reaching 25 meV at 3 kbar; the intensity increases 2–3 times as well. Numerical calculations were carried out on the band structure of the investigated heterostructures under compression along the [110] axis, which indicate the increase in the effective band gap in the quantum well (QW) GaAsyP1 − y, with a pressure coefficient of about 8.5 meV/kbar and reduction of the barrier height at the boundaries of the QW. The calculations predict the possibility that light and heavy holes crossover at pressures above 4.5–5 kbar. The increase in the effective band gap completely describes the experimental data on the shift of the electroluminescence spectra. The mixing of light and heavy holes when approaching the band crosspoint is the probable cause of an increase in the intensity of radiation under uniaxial compression.

Influence of pressure on the energy spectrum of low stage graphite intercalation compounds

Abstract The Li and Ba atoms were intercalated into the Van der Waals gap of Bi 2 Te 3 single crystals of n- and p-types. The resistivity, the Hall effect and the Shubnikov-de Haas effect were investigated in host single crystals and after an intercalation. The scattering of carriers is connected preferentially with acoustic phonons and does not change after intercalation. The mobility does not fall after intercalation as it does after doping the samples. The intercalation of metallic atoms causes the change in carrier concentration and, hence, the Fermi energy. But the intercalated samples possess the same energy spectrum as the host material.

Investigation of the character of the exchange interaction in the system Hg1−xMnxSe

The band structure, size quatized levels, and wave functions in the conduction and valence bands of strained n-AlxGa1 − xAs/GaAsyP1 − y/p-AlxGa1 − xAs (y = 0.84) heterostructures are calculated numerically upon a uniaxial compression along the [110] direction. The calculation indicates a sublinear increase of the effective optical gap in the GaAs0.84P0.16 quantum well, strong mixing of states of light and heavy holes, and merging of the corresponding ground states in the quantum well of the valence band under a pressure of 4.5–5 kbar. The calculation of matrix elements of the electron-photon interaction operator for a system of possible interband transitions permits one to determine the optical gain for the TE and TM modes. The increase in this coefficient by two to fourfold under uniaxial compression agrees with the previously published experimental data on the increase of the electroluminescence intensity.

The methastable electronic states in Pb1−xSnxTe alloys

The structure and electron properties of NanC60 (n = 2, 3) sodium fullerides synthesized from simple compounds in toluene were studied. It was shown that Na2C60 fulleride forms a face-centered cubic lattice at temperatures above 300 K. As the temperature is lowered, the phase transition to a structure with a simple cubic lattice takes place. The temperature dependences of the properties of Na3C60 with a more complex structure exhibit features that are presumably due to sodium atom redistribution in the Na3C60 fulleride lattice and the formation of sodium ion clusters.

Magnetoresistance and Hall Effect in Bi2Te3〈Sn〉 in Ultrahigh Magnetic Fields and under Pressure

The photoluminescence, magnetoresistance, Shubnikov-de Haas and Hall effect have been investigated in short period InAs/GaAs superlattices with different numbers of periods (3⩽N⩽24) and a total thickness of 14nm as a function of InAs layer thickness Q in the range 0.33⩽Q⩽2.7 monolayer (ML). These superlattices represent a quantum well with average composition In0.16Ga0.84As. Photoluminescence intensity and electron mobility enhancement occur when the InAs layer thickness Q is equal to 0.33 or 2.0ML. When Q⩾2.7ML, quantum dots are formed. The mobility of electrons and the anisotropy of resistivity do not depend monotonically on the thickness Q of InAs layers.