Band structure and electronic properties of mercury chalcogenide alloys containing iron

Abstract

Recent results obtained on Fe-based diluted magnetic semiconductors (DMS’s) are reviewed focusing on Hg1−xFexSe, where the Fe ions introduce donor states energetically coincident with the conduction band. These states can pin the Fermi level, producing samples in which the electron concentration is remarkably stable with time. The crystal growth methods and the magnetic properties are briefly presented. A discussion of the band structure and the position in energy of Fe-related donors in Hg1−xFexSe as a function of temperature and alloy composition is also given. Experimental evidence supporting the general picture of the band structure includes synchrotron radiation and ultraviolet photoemission spectroscopies, magnetoreflectivity, Hall effect, and Shubnikov–de Haas and de Haas–van Alphen effects. An anomaly in the low-temperature electron mobility in Hg1−xFexSe (0.0003≤x≤0.01), consistent with low Dingle temperatures seen in quantum oscillatory effects, is also discussed. A hypothetical explanation of the enhanced mobility relies on the spatial ordering of charges within the ionized donor system. Useful new features, related to the independent control over the band gap and Fermi energy in Fe-based DMS’s, are also presented.