HgSe Based Mixed Crystals Doped with Fe Resonant Donors

The article reviews the physical properties of semimagnetic semiconductors of the type Hg$\text{}_{1-x-y}$Fe$\text{}_{x}$A$\text{}_{y}^{II}$Se$\text{}_{1-z}$B$\text{}_{z}^{VI}$ and Hg$\text{}_{1-x-y}$Fe$\text{}_{x}$Mn$\text{}_{y}$Se. Optical, magnetooptical, transport and magnetotransport experiments showed that in Hg$\text{}_{1-x}$Fe$\text{}_{x}$Se substitutional iron forms a resonant donor state whose energy is superimposed on the conduction band continuum. Resulting anomalous properties of electron scattering rate, i.e. strong enhancement of electron mobility (or drop of Dingle temperature), which occur in Hg$\text{}_{1-x}$Fe$\text{}_{x}$Se at low temperatures in a certain Fe concentration range, are described. Next, theoretical models describing this anomalous reduction of the scattering rate are discussed. The description of thermomagnetic, optical, magnetooptical and magnetic properties of Hg$\text{}_{1-x}$Fe$\text{}_{x}$Se, with emphasis on features originating from the peculiar iron level position in the band structure of Hg$\text{}_{1-x}$Fe$\text{}_{x}$Se, conclude the first part of the present paper. In the second part the physical properties of the semiconducting alloys Hg$\text{}_{1-x}$Mn$\text{}_{x}$Se:Fe, Hg$\text{}_{1-v}$Cd$\text{}_{v}$Se:Fe, Hg$\text{}_{1-x}$Zn$\text{}_{x}$Se:Fe, HgSe$\text{}_{1-x}$Te$\text{}_{x}$:Fe and HgSe$\text{}_{1-x}$S$\text{}_{x}$:Fe are described. In particular, the dependence of the position of the Fe resonant donor state in the band structure on the crystal composition is discussed. The values of predicted Γ$\text{}_{6}$ and Γ$\text{}_{8}$ band offsets between HgSe and CdSe, HgTe, MnSe and ZnSe are given. The considerable attention is paid to the discussion of the mechanism limiting the electron mobility in the mixed alloys. Finally, topics which have not been explicitly covered in this review are mentioned and open problems are discussed.