Electronic structure of diluted magnetic semiconductors Pb_{1–x –y}Ge_x Cr_y Te under pressure

The galvanomagnetic properties of Pb_{1–x –y} Ge_x Cr_y Te in the temperature range 4.2–300 K under variation of the alloy composition (x ≤ 0.13, y ≤ 0.05) and under hydrostatic compression (P ≤ 17 kbar) have been investigated. Pressure dependences of the electron concentration and Fermi energy were obtained. In the frame of the Kane dispersion relation theoretical dependences of electron concentration and Fermi energy were calculated and parameters of chromium impurity band were estimated. Magnetic field dependences of the Hall coefficient under variation of germanium content and under pressure were measured. It is shown, that existence of two conductivity mechanisms should be taken into account: conduction band conductivity and electron-type conductivity via chromium impurity band states. In terms of the two-band conduction model the main parameters of charge carriers were obtained. Experimental results are discussed taking into account the diagram of the electronic structure reconstruction under pressure, assuming finite capacity, electron filling and widening of the impurity band. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)