J. Phys. IVFrance 109 (2003) 123 (D EDP Sciences, Les Ulis DOI: 10.1051/jp4:20030660 Photoacoustic study of Cdl,-yBexMnyTe mixed crystals J. Zakrzewski, F. Firszt, S. Legowski, H. Mçczynska, A. Marasek and M. Pawlak Instytut Fizyki, Uniwersytet Mikolaja Kopernika, Ul. Grudziadzka 5-7, 87-100 Torun, Poland Abstract. Quaternary diluted niagnetic semiconductors Cdl,-yBe,,MnyTe obtained by Bridgmaii method for x-0. 01 and 0 y : 0. 15 were investigated. The photoacoustic spectroscopy with a piezoelectric transducer was employed to evaluate the energy gaps of Cd1. x_yBe, MnyTe blùk mixed crystals al room temperature. The increase of the energy gap with increasing x value has been observed. Characteristic features of amplitude and phase photoacoustic spectra were discussed. 1. INTRODUCTION Recently diluted magnetic semiconductors (DMS) are subject to many studies. Among II-Vt di!uted magnetic semiconductors Cdl-, MnxTe shows very interesting properties due to a strong s, p-d exchange interaction between electrons, holes and ion Mn électrons. Reflectivity [1] and photoacoustic [2] measurements show that the fundamental band gap ofCdi.xMnxTe shifts linearly with Mn concentration for 0x<0.7. M. M. Moriwake et al [3] observed for x >: 0. 37 strong absorption below the band gap which is ascribed to Mn intraionic transition. For Cdi-xMnxTe temary mixed crystals the band gap 160' E=1. 5eV 6 Hz increases and the lattice constant decreases with 120-, "' : :'1 E=1. 5eV 6 Hz increasing Mn content. 80 : : : t,. In the case of quaternary diluted magnetic 40 : :,. semiconductor the magnetic properties do not °,---- change with the variation of lattice parameters fë ----!--"" : when the second non magnetic component of the 120 36 Hz alloy is incorporated. This was observed for Cdi- g' 80 - -' ' - = x,, MgxMn,, Te [4]. It was found in the case of D 40 Cd,-, MnxTe, that the average ionicitv of Mn-Te S o- .-' '.\. '"---.-. - i bonding increases with increasing of Mn content-40 due to the influence ofthe nearest Mn ion [5].i60 126. z < This results in a higher transition energy for 120 : 126 ho crystals with higher Mn concentration [6]. Similar 80 effect was observed for Cdj,-, MnxMgyTe when 40 Mn content is kept constant but Mg _ ....--' \._______ j concentration increased. The quaternary compounds have more .21.416 8 controlled parameters than the ternary ones and Energy eV,' for this reason a higher possibility of theirF'igjrel: Phase (solid)and amplitude (dots) spectra application in constructions of optoelectrical of CdTe for difîcrcnt modulation frequencies