Transition-metal impurities in semiconductors and heterojunction band lineups

Langer, Judith; Delerue, Christophe; Lannoo, M.; Heinrich, H.

doi:10.1103/physrevb.38.7723

Cited by 201 publications

(92 citation statements)

References 158 publications

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“…5͑b͔͒, as observed before by Sauer et al, 14 and Gwinner and Labusch. 25 The linewidth of the high-energy line is approximately 30 meV at T ϭ100 K. According to the model proposed by Suezawa et al 15 following the earlier interpretation by Gwinner and by Langer et al 26,27 Following the model of Suezawa et al 15 the change of transition energy of D1, which we observe in experiment can be ascribed mainly to the downshift of the shallow level following the valence band perturbation. Its accurate position has been found by fitting with Gaussianshape lines.…”

Section: Deep-level-related Bandmentioning

confidence: 96%

Experimental investigation of band structure modification in silicon nanocrystals

et al. 2001

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Experimental studies of size-related effects in silicon nanocrystals are reported. We present investigations carried out on nanocrystals prepared from single-crystal Si:P wafer by ball milling. The average final grain dimension varied depending on the way of preparation in the range between 70 and 230 nm. The ball milling was followed by sedimentation and selection of the smallest grains. The initial grain size distribution was measured by scanning electron microscopy. Further reduction in size was achieved by oxidation at 1000°C which creates a silicon dioxide layer around a silicon core. The oxidation process was monitored by transmission electron microscopy and the growth speed of SiO 2 was estimated in order to model the grain size of nanocrystals. Crystallinity of silicon grains was confirmed by x-ray diffraction and by transmission electron microscopy using a bright/dark field method and selected area diffraction pattern. In the silicon nanocrystals the electron energy levels are shifted which was observed separately for conduction band, valence band and energy band gap. Electron paramagnetic resonance was applied to investigate variation of the conduction band minimum by monitoring its influence on the hyperfine interaction of phosphorus shallow donor. On the basis of these results an explicit expression for conduction band upshift as a function of average grain size has been derived. Information about the downshift of the valence band was obtained from measurements on a photoluminescence band related to a deep to shallow level transition. A perturbation of a few meV for grain sizes of the order about 100 nm has been observed. Internal consistency of these findings has been examined by investigation of the photoluminescence band due to an electron-hole recombination whose energy is directly related to the band gap of silicon.

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Section: Deep-level-related Bandmentioning

confidence: 96%

Experimental investigation of band structure modification in silicon nanocrystals

et al. 2001

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“…According to the Anderson model, the character of magnetic impurities in solids results from a competition between (i) hybridization of local and extended states, which tends to delocalized magnetic electrons and (ii) the onsite Coulomb interactions among the localized electrons, which stabilizes the magnetic moment in agreement with Hund's rule. Lannoo andHeinrich, 1988 andZunger, 1986. ) of the host II-VI and III-V compounds.…”

Section: Magnetic Impurities In Semiconductorsmentioning

confidence: 99%

Diluted Ferromagnetic Semiconductors—Theoretical Aspects

Dietl

2007

Handbook of Magnetism and Advanced Magnetic Materials

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This chapter reviews theoretical understanding of ferromagnetic response that has been detected in diluted magnetic semiconductors (DMS). Particular attention is paid to those ferromagnetic DMS in which no precipitation of other crystallographic phases has been observed. It is argued that these materials can be divided into three categories. The first consists of (Ga,Mn)As, heavily doped p‐(Zn,Mn)Te, and related compounds. In these solid solutions, the theory built on p–d Zener's model of hole‐mediated ferromagnetism and on either the Kohn‐Luttinger kp theory or the multiorbital tight‐binding approach describes qualitatively, and often quantitatively, thermodynamic, micromagnetic, optical, and transport properties. Moreover, the understanding of these materials has provided a basis for the development of novel methods enabling magnetization manipulation and switching. To the second group, belong compounds in which a competition between long‐range ferromagnetic and short‐range antiferromagnetic interactions and/or the proximity of the localization boundary lead to an electronic nanoscale phase separation that results in characteristics similar to colossal magnetoresistance oxides. Finally, in a number of compounds a chemical nanoscale phase separation into the regions with small and large concentrations of the magnetic constituent is present. Methods of controlling the spinodal decomposition and possible functionalities of these systems are outlined.

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“…For low carrier densities, these valence band holes will be bound to the Mn ion, leading to shallow acceptor levels. This model of carrier-induced ferromagnetism is now fairly well established for (Ga,Mn)As as a result of electron paramagnetic resonance experiments [7], xray magnetic circular dichroism measurements [8,9], and magneto-transport data [10-13].The acceptor impurity levels of Fe and Co [2,3,6,4] are unlikely to lead to high valence band hole concentrations in arsenides or antimonides, as shown in Fig. 1.…”

mentioning

confidence: 99%

Theoretical Models of Ferromagnetic III‐V Semiconductors

et al. 2003

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Recent materials research has advanced the maximum ferromagnetic transition temperature in semiconductors containing magnetic elements toward room temperature. Reaching this goal would make information technology applications of these materials likely. In this article we briefly review the status of work over the past five years which has attempted to achieve a theoretical understanding of these complex magnetic systems. The basic microscopic origins of ferromagnetism in the (III,Mn)V compounds that have the highest transition temperatures appear to be well understood, and efficient computation methods have been developed which are able to model their magnetic, transport, and optical properties. However many questions remain.It is hoped that the emerging field of semiconductor spintronics, which studies the controlled flow of charge and spin in a semiconductor, will lead to the development of new non-volatile, high-density, and high-speed information technologies. An important milestone in this field was the discovery five years ago of ferromagnetism in Mn-doped, p-type GaAs observed at temperatures in excess of 100 Kelvin [1]. Ferromagnetism at room temperature with full participation of itinerant carriers would be a major breakthrough in semiconductor spintronics. With this aim, intensive material research is currently in progress on transition metal doped III-V semiconductors. In this brief review we present a snap shot of the theoretical part of this endeavor, which has progressed hand in hand with experimental developments.A qualitative picture of the electronic structure of III-V diluted magnetic semiconductors (DMSs) was proposed by Dietl and coworkers [2,3]. Their model is based on the internal reference rule [6] which states that energy levels derived from the d-shell of the magnetic ion are constant across semiconductor compound families with properly aligned bands. The application of this rule to III-V materials is illustrated in Fig 1 for ionized magnetic impurities substituted on cation sites [2][3][4][5]. The position of the A 2 level for Mn in GaAs, deep in the valence band, suggests that Mn in GaAs is 2+, that its d-shell is occupied by five electrons, and that incorporation of Mn in this and many other (III,Mn)V compounds will result a large density of valence band holes that can mediate ferromagnetic coupling between the S = 5/2 Mn local moments. For low carrier densities, these valence band holes will be bound to the Mn ion, leading to shallow acceptor levels. This model of carrier-induced ferromagnetism is now fairly well established for (Ga,Mn)As as a result of electron paramagnetic resonance experiments [7], xray magnetic circular dichroism measurements [8,9], and magneto-transport data [10-13].The acceptor impurity levels of Fe and Co [2,3,6,4] are unlikely to lead to high valence band hole concentrations in arsenides or antimonides, as shown in Fig. 1. The possible coexistence of acceptor and neutral magnetic impurities suggests that a ferromagnetic double-exchange mechanism can dominate ...

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Transition-metal impurities in semiconductors and heterojunction band lineups

Cited by 201 publications

References 158 publications

Experimental investigation of band structure modification in silicon nanocrystals

Experimental investigation of band structure modification in silicon nanocrystals

Diluted Ferromagnetic Semiconductors—Theoretical Aspects

Theoretical Models of Ferromagnetic III‐V Semiconductors

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