The Study of Optical Spectrums (of Absorption and Reflexion) in Semi-Magnetic Semiconductors of Cd_(1-x)Mn_xTe Type

摘要

Solid solutions from the Cd_(1-x)Mn_xTe category are semiconducting materials with a very good perspective of being used in optoelectronics and nanoelectronics. Characteristic for the absorption spectrums of the semi magnetic solid substances Cd_(1-x)Mn_xTe is the presence, at low temperatures, of a well marked frontier, that moves towards higher energies with the increase of the x component. In the long wavelength domain of the spectrum there is a series of maximum values, associated with the absorption through the formation of free excitons. An observation has been made that in solid solutions Cd_(1-x)Mn_xTe (0,0≤x≤0,5) the photon–exciton interaction is very strong at temperatures around T=78 K. The acceptor level, determined by this band, is displaced to the extremity of the valence band with ～30 meV at T=293 K and –40 meV at 78 K. From analyzing the structure of the reflection spectrum we determined the forming mechanism of the edge of the intrinsic adsorption band with the energies of the maximum exciton values. For the thin layers adsorption spectrums, grown on a mica base at a temperature of 680 K through discrete evaporation of the Cd_(0,5)Mn_(0,5)Te crystals, the edge of the adsorption band is located at the energy level ～1,99 eV and 2,13 eV for the temperatures 293 K and 78 K respectively. In the adsorption spectrum of the thin layers there is an adsorption threshold at～1,7eV (T=293 K) and 1,84 eV (T=78 K). The given level of impurity, formed of electrons that make transitions from the impurity level in the conductivity level, is situated at ～0,3 eV from the maximum of the valence band.