The electronic structure and magnetic properties of GeTe-based dilute magnetic semiconductors (DMS) are investigated by the Korringa-Kohn-Rostoker Green's function method and the projector augmented wave method. Our calculations for the formation energies of transition metal impurities (TM) in GeTe indicate that the solubilities of TM are quite high compared to typical III-V and II-VI based DMS and that the TM doped GeTe has a possibility of room temperature ferromagnetism with high impurity concentrations. The high solubilities originate from the fact that the top of the valence bands of GeTe consists of the Te-5p anti-bonding states which are favorable to acceptor doping. (Ge, Cr)Te system shows strong ferromagnetic interaction by the double exchange mechanism and is a good candidate for DMS with high Curie temperature. Additionally, in the case of (Ge, Mn)Te with the d(5) configuration, by introducing the Ge vacancies the p-d exchange interaction is activated and it dominates the antiferromagnetic superexchange, resulting in ferromagnetic exchange interactions between Mn. This explains recent experimental results reasonably. Based on the accurate estimation of the Curie temperatures by Monte Carlo simulation for the classical Heisenberg model with the calculated exchange coupling constants, we discuss the relevance of the TM doped GeTe for semiconductor spintronics.
The development of flexible thermoelectric devices is gradually attracting increasing attention, particularly in the field of material design. In this study, we use first-principles calculations combined with Boltzmann equations to study the electronic and transport properties of Ag2S1− xSe x, a key material with many important properties and extraordinary ductility, as well as a wide range of thermoelectric applications. The effect of Se alloying on the electronic structure of Ag2S and defect formation is investigated, and the role of alloying in increasing the n-type carrier concentration is discussed. The electron–phonon coupling approximation is used to reproduce the experimentally observed transport properties reasonably well, which shows that this scattering model is suitable for predicting the transport properties of semiconductors in thermoelectric applications.
Recently, Fe-doped semiconductors have been attracting much attention as ferromagnetic semiconductors due to the possibility that they may exhibit high Curie temperatures and low power consumption and that they may be useful for high-speed spin devices. High Curie temperature ferromagnetism has been observed in Fe-doped InAs, from which both n- and p-type ferromagnetic semiconductors can be fabricated. In order to obtain a higher Curie temperature than that of (In, Fe)As, we have focused on GaSb and InSb as host semiconductors. We have investigated their electronic structures, magnetic properties, and structural stability by using the Korringa-Kohn-Rostoker Green's function method within density functional theory. We have found that (Ga, Fe)Sb and (In, Fe)Sb show complex magnetic properties, which are determined by the correlation between magnetic exchange coupling constants and chemical pair interactions. Isoelectronic Fe-doped GaSb and InSb have strong antiferromagnetic interactions due to the super-exchange mechanism. By shifting the Fermi level–i.e., by n- or p-type doping–(Ga, Fe)Sb and (In, Fe)Sb can be made to undergo a magnetic transition from antiferromagnetic to ferromagnetic ordering. This transition can be well understood in terms of the Alexander-Anderson-Moriya mechanism. Our calculations indicate the possibility of manipulating (Ga, Fe)Sb and (In, Fe)Sb to achieve high Curie temperatures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.