Stanislaw Legowski

Photoacoustic study of Zn1−xBexSe mixed crystals

The photoacoustic spectroscopy (PAS) with piezoelectric transducer was employed to evaluate band gap energies in Zn1−xBexSe mixed crystals of different composition. The spectra were measured at 300 K and 90 K using continuos wave excitation. The Jackson-Amer model of photoacoustic effect was applied. The increase of the band-gap energy with increasing Be content is observed. The photoacoustic results are compared with those from photoluminescence spectra.The photoacoustic spectroscopy (PAS) with piezoelectric transducer was employed to evaluate band gap energies in Zn1−xBexSe mixed crystals of different composition. The spectra were measured at 300 K and 90 K using continuos wave excitation. The Jackson-Amer model of photoacoustic effect was applied. The increase of the band-gap energy with increasing Be content is observed. The photoacoustic results are compared with those from photoluminescence spectra.

Growth, luminescence and photoacoustic characterization of Zn 1−x−y Be x Mn y Se crystals for optoelectronic applications

Zn1-x-yBexMnySe solid solution is a very interesting semiconductor because it is promising material for future application in spintronics as a spin filter layer as well as in memory technology. The energy gap of BeSe is larger that that of ZnSe while the lattice constant of BeSe is lower than that of ZnSe. Both of them crystallize in sphalerite structure. By changing the content of beryllium it is possible to obtain material with different energy gap and lattice constant, matched to different substrates. For construction of optoelectronic devices the multilayer structures are commonly used. In such technology knowing of optical and thermal diffusivity of layer component materials is very important. This work deals with photoacoustic and photoluminescence studies of bulk Zn1-x-yBexMnySe mixed crystals.

Elastic and elasto-optic properties of Zn1-xBexSe mixed crystals by Brillouin scattering method

In this paper we report experimental results concerning the elastic and elastooptic properties of Zn1-xBexSe mixed crystals grown by high pressure Bridgman technique. Using Brillouin scattering method some of the elastic and elastooptic constants of Zn1-xBexSe crystals with different Be content have been determined at room temperature. It has been revealed that the elastic and elastooptic properties strongly depend on the content of Be.

Study of Zn1-xMgxSe and Zn1-xBexSe semiconducting crystals by Raman scattering

Wide gap II-VI mixed crystals containing Mg and Be are recently studied extensively for their application in constructing blue-green laser diodes. This work deals with experimental study of optical modes in Zn1-xMgxSe and Zn1-xBexSe semiconductors using Raman scattering method. Measurements have been performed at room and liquid nitrogen temperatures for Zn1-xMgxSe crystals with Mg content in the range 0 < x < 0.34 and for Zn1-xBexSe with Be content in the range 0 < x < 0.26. From polarized Raman spectra longitudinal and transverse optical modes corresponding to ZnSe- and MgSe-like modes in Zn1-xMgxSe and to ZnSe- and BeSe-like modes in Zn1-xBexSe were determined. These lattice vibrations can be described by the modified random element isodisplacement model.

Photoluminescence and structural properties of selected wide-gap II-VI solid solutions

This work presents results of investigations of photoluminescence and structural properties of ternary Zn1-xBexSe, Cd1-xMgxSe, Zn1-xMgxSe and quaternary Cd1-x-yMgxZnySe, Zn1-x-yBexMgySe, Zn1-xMgxSe1-ySey mixed crystals. These crystals were grown from the melt by the high-pressure Bridgman method. Zn1-xMgxSe and Zn1-xSrxSe were also obtained by annealing of ZnSe crystals in evacuated quartz ampoules containing Mg or Sr metal. It has been found that admixing of Mg into ZnSe favors the formation of wurtzite Zn1-xMgxSe while Be-sphalerite Zn1-xBexSe structures. Low temperature (40 K) photoluminescence spectra consist of exciton, edge and deep levels emission bands. For most of investigated crystals the emission corresponding to the highest photon energy line in luminescence spectrum is observed up to room temperature.

Growth and characterization of Zn1-xMgxSe mixed crystals

This paper deals with experimental study of structural and luminescent properties of Zn1-xMgxSe mixed crystals in the x range from 0.0 to 0.615. These crystals were grown by the high pressure Bridgman method. X-ray diffraction and high resolution electron transmission microscope measurements reveal that for magnesium concentration lower than about x equals 0.18 Zn1-xMgxSe crystallize in sphalerite structure but for higher -- in wurtzite one. The formation of 4H phase and some other polytypes has been found at the composition close to the phase transition. From investigations of luminescence and reflection spectra the dependence of the exciton transition energy on composition has been determined. In-Zn0.9Mg0.1Se-Au structure has been fabricated. Blue-violet, green and yellow electroluminescence was observed in the temperature range from 40 K to room temperature.

Characterization of Zn1-xMgxSe mixed crystals by photoacoustic method

The photoacoustic spectroscopy with a piezoelectric transducer was employed to evaluate the band gaps of a series of Zn1- xMgxSe mixed crystals of different composition. The measurements were performed at 300 K, 90 K and 6 K. The Jackson-Amer model of photoacoustic effect for thermally thin and optically thick samples was applied. For samples of x greater than 0.18 (wurtzite structure) subgap optical absorption was observed.