Zn_1-x-yBe_xMn_ySe semiconductor is an interesting material for spintronics as a spin filter layer with possible applications in memory technology. Changing of the content of beryllium allows obtaining materials with different energy gap and lattice constant, matched to different substrates. For application in multilayer technology, knowing of optical and thermal properties of such material is very important. Up to date there are only a few papers concerning Zn_1-x-yBe_xMn_ySe material. This work deals with photoconductivity, luminescence and photoacoustic investigations of bulk Zn_1-x-yBe_xMn_ySe mixed crystals.

Zn_1-x-yBe_xMn_ySe solid solutions were grown from the melt by the modified Bridgman method. Photoluminescence and photoluminescence-excitation spectra were measured in the temperature range from 30K to room temperature. Photoacoustic spectra were measured applying the mechanically chopped radiation from the xenon lamp after passing through monochromator. The PA signal was detected using an open photoacoustic cell with PZT transducer and lock-in technique. Photoconductivity and transmission spectra were carried out at room temperature.

Photoluminescence spectra at low temperatures of Zn_1-x-yBe_xMn_ySe samples with Mn content not exceed 5% consist of relatively weak exciton line, shallow donor-acceptor band (edge emission) and the main yellow luminescence band positioned at the energy about 2.05 eV associated with Mn ions. The exciton line was observed in samples with Mn content up to 0.2. For larger concentration of manganese only yellow emission is observed at temperatures from 35K to room temperature. The photoluminescence-excitation spectra, when the emission is detected at 2.05 eV, consist of four clearly resolved components, interpreted as due to transitions from the ground ⁶A₁(⁶S) state of Mn to different excited states associated with crystal field splitting.

The piezoelectrically detected photoacoustic spectra were interpreted using Jackson and Amer theory. From the spectral dependence of the amplitude and phase of photoacoustic signal the variation of energy gap with composition was determined. It was found that the influence of Mn on the value of energy gap is much lower than Be. Very important parameter characterizing semiconductors is the thermal diffusivity, which describes the process of thermal transport in semiconductors and characterizes the time required to establish the thermal equilibrium in the investigated material. In this work thermal diffusivity was determined from the dependence of photoacoustic signal on modulation frequency of radiation illuminating the sample. It was calculated with the method of fitting of experimental data to theoretical model developed by Blonskij et al.

The excitation spectra of photoconductivity were measured in the energy range from 0.8 eV to 3.6 eV and compared with PA and PLE spectra.

The photoluminescence-excitation spectra provide information concerning radiative recombination processes in semiconducting materials, while photoacoustic spectral characteristics are directly related to the nonradiative transition paths. Photoconductivity measurements can provide information on both, radiative and nonradiative recombination processes of excited carriers. Some fundamental parameters characterizing semiconducting materials obtained for Zn_1-x-yBe_xMn_ySe with the mentioned above different methods were compared and discussed.

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1. Lattice parameters of a wurtzite-type (Zn,Mg)Se crystal as a function of temperature
2. Study of the third order nonlinear optical properties of Zn_1-xMg_xSe and Cd_1-xMg_xSe crystals
3. Growth and properties of Zn_1-x-yBe_xMn_ySe Crystals