Optoelectronic Application of the 3C-Silicon Carbide with

Article pubs.acs.org/JPCC

Optoelectronic Application of the 3C-Silicon Carbide with Substitutional VIII-Group Atoms C. Tablero* Instituto de Energía Solar, E.T.S.I. de Telecomunicación, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain S Supporting Information *

ABSTRACT: The silicon carbide semiconductor forms stable and longrange ordered structures with interest in technology because of their optoelectronic properties, hardness, large thermal conductivity, and chemical stability. The optoelectronic properties can be potentiality improved by the insertion of intermediate states into the energy band gap. We explore this possibility using VIII-group transition metal impurities carrying out first-principles calculations. In some cases, the impurity introduces a deeper band into the host energy band gap for ferromagnetic and antiferromagnetic spin alignments. These intermediate bands could split into two sub-bands through a site deformation around the impurities or a Mott-Hubbard metal−insulator transition. We have extended the study in order to analyze these possibilities. From our results, these effects or a combination of them do not split the bands in the energy band gap. Therefore, these deeper bands open up more photon absorption channels and could therefore increase the solar-light absorption with respect to the host in solar-cell devices.

1. INTRODUCTION Silicon carbide (SiC) has attracted much interest in technology as a wide-gap semiconductor in high-power electronic devices.1 It features large electronic band gaps, hardness, large thermal conductivity, and chemical stability. SiC is well-known for showing polytypes of various stacking sequences with the same chemical composition. Among the many polytypes, the most technologically important ones are 3C-SiC (also called β-SiC), 4H-SiC, and 6H-SiC (also called α-SiC). In all polytypes, every atom is surrounded by four atoms of the other species. The cubic modification 3C-SiC has a zinc-blend structure, thus being the type with the closest structural relationship to both diamond and elemental Si. The band structure of 3C-SiC has been estimated from optical absorption and reflection,2 luminescence,3 soft X-ray emission,4 and X-ray photoelectron5 spectra. In developing a material for use in device applications, it has been found that deep energy levels in the forbidden energy gap play an important role. These midgap levels are produced by extrinsic and intrinsic impurities and defects, as isolate Si and C vacancies in SiC.6 It determines many of the most important parameters of semiconductor devices. Deep centers in the bulk of a semiconductor can act as carrier recombination or trapping centers and affect the performance of electronic and optoelectronic devices. They also have an effect on the lifetime and diffusion length of minority charge carriers, the efficiency of light-emitting diodes and photodetectors, the gain of transistors, etc. Controlled n- and p-type doping can be carried out during crystal growth, and the selective doping of both © 2013 American Chemical Society

donor- and acceptor-type impurities can be carried out through ion implantation.7,8 Impurity atoms in SiC substitute either the silicon or carbon sublattice. Nitrogen as well as other donor impurities, such as phosphorus, occupy the carbon sites.9−11 Boron may substitute the carbon sublattice or occupy either the carbon or the silicon site (or both of them) in order to minimize the total free energy of the system. Aluminum atoms substitute only the silicon sublattice.12 SiC, an indirect gap material, has several luminescence bands involving transitions between impurities (for example, between N and Al levels) and between free and bound exciton states. As a consequence, SiC light emitting diodes can cover the whole visible spectrum.7 Silicon carbide is another semiconductor that has also been considered a possible candidate for spintronic applications. Experimental studies have demonstrated a ferromagnetic response in Ni-, Mn-, and Fedoped SiC.13,14 Depending on the impurity concentration the properties may vary from localized defect states at low concentration (impurity-doping) to the formation of an energy band at high concentration (impurity-alloying). The deep levels in the middle of the band gap semiconductor for impurity-doping could lead to an intermediate band (IB) for impurity-alloying. If the IB is partially full, i.e., the Fermi energy crosses the IB, the electronic structure of this material has simultaneous characterReceived: July 25, 2013 Revised: September 16, 2013 Published: September 30, 2013 21949

dx.doi.org/10.1021/jp4074015 | J. Phys. Chem. C 2013, 117, 21949−21954

The Journal of Physical Chemistry C

Article

The calculations of the electronic structure were carried out preserving the experimental atomic positions of the reference compound for the largest supercells and relaxing all the cell atoms for the smallest. For this purpose, the conjugate gradient algorithm is used, in accordance with the calculated quantum mechanical forces. Relaxation to the absolute energy minimum is considered accomplished when the forces on the atoms fall below 0.004 eV ·Å−1. In the currently used exchange and correlation functional, the interactions are treated in a mean field approach, which is not suitable to describe the correlation effects properly. Therefore, a further extension beyond the GGA was carried out using the GGA+U method,22,23 including an orbital-dependent oneelectron potential to account explicitly for the important Coulomb repulsions not treated adequately in the GGA approach. The exchange and correlation energy depends on the GGA+U representation. Thus, the value of U depends on the choice of the orbitals on which the correction is applied, on the way the orbital occupations are computed, and on the GGA +U implementation chosen.23−26 In this work, we applied the orbital-dependent one-electron potential to the d-TM states using the GGA/LDA+U formalism described in refs 23 and 24 with U = 5 eV. The knowledge of the imaginary part of the dielectric function allows the calculation of other optical functions using the Kramers−Kronig relationships. The imaginary dielectric function is related to the energies (Eμ,k) and the occupations ( fμ,k) of the μ bands, and the transition dipole matrix elements pμ,λ = ⟨μ,k|p̂|λ,k⟩ between the μ and the λ bands at point k of the Brillouin zone:

istics of semiconductor (the valence band (VB) and conduction band (CB) of the host semiconductor) and metal (the metallic IB). Because of the metallic IB properties (into the energy band gap and partially full), this IB could split into two sub-bands through a site deformation around the impurities or a Mott− Hubbard metal−insulator transition. If this partially full IB is stable, i.e., it is not split into two sub-bands, this compound can be used for optoelectronic devices. For example, the metallic IB opens up two additional channels for the photon absorption: from the VB to IB, and from the IB to CB (Figure 1). It can

Figure 1. Structure of the simplified band gap diagram in equilibrium of an intermediate band solar cell.

generate, by solar-light absorption, additional carriers (holes in the VB and electrons in the CB) thereby increasing the efficiency in solar-cell devices with respect to the single-gap host semiconductor.15 In order to explore the potential application to optoelectronic and spintronic devices, we are going to analyze the electronic properties of the substitutional VIII-group atoms in the 3C-silicon carbide. The study is carried out using firstprinciples methods. Because of the characteristics of the intermediate states in the band gap, the possible metal− insulator transitions are examined.

e 2( E ) ≈

1 E2

∫ (2dπk)3 ∑ ∑ ∑ pμλ (k)|2 [fμ,k k⃗

μ

− fλ , k ]δ

λ

(Eλ , k − Eμ , k − E)

3. RESULTS AND DISCUSSION The indirect band gap of 3C-SiC obtained with supercells from 2 to 216 atoms is 1.36 eV. This value is lower than the experimental data (2.2−2.4 eV27). This well-known GGA energy gap underestimation problem is similar to other theoretical data in the literature (∼1.2−1.3 eV28,29). However, in spite of this underestimation problem, the pressure variations of the bandgaps in semiconductors have been correctly described with this methodology.30 The transition metal atomic radii are much closer to Si than to C. Thus, according to the atomic radii, the substitutional TM impurities preferably occupy the Si sites in the SiC crystal. In this way, a lower lattice distortion would be required in the case of Si site substitution. This was found in our study, in accordance with other results in the literature.31,32 Thus, henceforth we will focus on the Si substitution by M = Fe, Co, and Ni. We have carried out first-principles calculations for the ferromagnetic (FM) and antiferromagnetic (AFM) M-doped silicon carbide (M = Fe, Co, and Ni) using GGA. One of the main effects of substituting Si host atoms by M in the electronic structure of the SiC host is to generate a partially full intermediate band (IB) in the energy band gap for both the FM and AFM spin alignments (Figures 2−4). For the FM state only, an IB with spin-up character is present, whereas for the AFM state, both spin characteristics are present because of the

2. CALCULATIONS The electronic properties were obtained using first principles within the framework of the density functional formalism. The standard Kohn−Sham16 equations are solved self-consistently with a private modification of the SIESTA code17 using a confined pseudoatomic orbitals18 basis set. For the exchangecorrelation potential, we used the generalized gradient approximation (GGA) from Perdew, Burke, and Ernzerhof.19 The standard Troullier−Martins20 pseudopotential is adopted and expressed in the Kleinman−Bylander21 factorized form. All calculations were made considering spin polarization and periodic boundary conditions. The AB1−xMx alloys (A,B = C or Si, and M = Mn, Fe, Co, Ni) were studied using 64- and 216-atom supercells. The doping of x = 1/32 (2/32) was obtained by replacing M by Si or C at the apex and/or face-center sites of the host supercells with 64 atoms; x = 1/108 (2/108) is similar, but with the 216 atom supercells. The number of atoms in the supercell N is related to the impurity concentration as ∼1022/N cm−3 approximately, i.e., ∼10−20−10−21 cm−3. In all of the results presented in this work, a double-ζ with polarization functions basis set has been used with periodic boundary conditions. Between 32 and 75 special k-points for the 64- and 216-atoms supercells are used depending on the size of the supercell in order to keep a constant k point density in the irreducible Brillouin zone (BZ). 21950



Article

magnetization of the Fe-doped SiC experimental samples can be attributed to two origins: ferromagnetic Fe3Si crystallites and ferromagnetic alignment of individual magnetic moments of the Fe3+ ions randomly substituting the Si sites of the sample. The contribution depends on the impurity concentration34 and on the synthesis route.35 Anyway, the presence of different phases (such as Fe3Si in SiC:Fe34,35 and Ni2Si in SiC:Ni36) can modify the observed magnetic properties. For the MSi substitution, the M site is tetrahedrally surrounded by the nearest four C neighboring atoms. The 5fold degenerate d-states of M impurity are split by the crystalline field into doubly degenerate de-states (dz2 and dx2−y2) and 3-fold degenerate dt-states (dxy, dxz, and dyz) in the tetrahedral coordination, whereas the s and p atomic orbitals of M have a and t tetrahedral symmetry respectively, i.e., sa and pt. The M atoms will interact mainly with the closest C atoms. Therefore, the crystal wave functions with t symmetry are formed mainly by the combination of the dt−pt M states, and by the states with t symmetry of the host (Ht): t ≈ αdt + βpt + γHt. These Ht states correspond mainly to the neighboring p-C states. However, the wave functions of the e symmetry are extended to the interstitial region. Therefore, the hybridization of the de TM states with the He symmetry host states of the VB is weak, and e states remain as nonbonding TM states: e ≈ de. In all cases the partially full IBs have t symmetry, i.e., t+-IB for FM and t-IB for AFM spin alignments (t+ = t− = t). For FM spin alignment, in addition to the partially full t+-IB, there is a full e−-IB between the VB and the IB for the CoSi substitution, and an empty t−-IB between the IB and the CB for the NiSi substitution. This is similar to what happens for the AFM spin alignment. In order to verify the previous analyses on the structure of these IBs, a study of the projected density of states (DOS) on atoms and states has been carried out. The results indicate that for both the FM and AFM spin alignments, these IBs are mainly made up of the dt-M and p-C orbitals of the nearest four neighbors and in a lower proportion by the pt-M orbitals. In particular, the contribution of these atomic states to the IB is, in decreasing order, dt-M ≈ p-C > pt-M for M = Fe substitution and dt-M > p-C > pt-M for the M = Co and Ni substitutions. According to the ionic model, when the transition metal M substitutes C or Si, four of its electrons are given to the bonds, thus forming the deep impurity level M4+ (dn), i.e., with an oxidation state +4: Fe4+ (d4), Co4+ (d5), and Ni4+ (d6). These electrons occupy the crystal wave functions with t and e symmetry made up through the combination of the d-M states and by the states of the host. The electronic configurations of these crystal states at the tetrahedral substitutional site are Fe4+(e0−e2+t2+), Co4+(e2−e2+t1+), and Ni4+(e2−e2+t2+). In all cases there is a partially full t+-IB for FM spin alignment (t-IB for AFM spin alignments). For the FM spin alignment, the total magnetization of the unit cell per M atom is 4 μB, 1 μB, and 2 μB for the FeSi, CoSi, and NiSi substitutions, in agreement with the previous configurations. From the results obtained using the GGA formalism, i.e., the presence of a partially full IB in the energy band gap, the correlation effects could be significant.37 As well as a narrowband Jahn−Teller deformation or Peierls distortion38 could also take place. In both cases, strong correlation or lattice distortion, the partially full IB could split into two bands, a full lower band and an upper empty band, i.e., a metal−insulator transition could happen.

Figure 2. Energy band structure for the FeSi (x = 0.062): (a) majority spin component of the FM spin alignment, (b) minority spin component of the FM spin alignment, and (c) AFM spin alignment. The Fermi energy has been chosen as zero energy in the figure.

Figure 3. Same legend as that in Figure 2, but for CoSi.

Figure 4. Same legend as that in Figure 2, but for NiSi.

symmetry of the up and down components. The Fermi energy is in the IB indicating that the IB is partially full. For all cases, these IBs have t symmetry. The energy differences per M atom between the AFM and FM configurations are 0.114/0.027/0.100 eV for Fe/Co/Ni, indicating that the FM spin alignment is slightly more stable than the AFM. It is in accordance with some of the experimental studies of Fe-doped SiC where ferromagnetic diluted magnetic semiconductor behavior in Fe-implanted 6HSiC is reported,13,14 and with theoretical studies on SiC:Fe nanotubes.33 At a lower M concentration, both FM and AFM states have close energies and may coexist. The observed 21951



Article

However, because of the larger contribution of the p-C orbitals of the nearest four neighbors of the M impurity, the correlation effects in the IB should be minimized because of a dilution effect24 of the self-interaction. The greater orbital correlation of the d-M states is reduced in the partially full IB as there are other orbital contributions with lower self-interaction (the p-C states). Also, because the dt-M and p-C orbitals of the nearest four neighbors contribute to the antibonding IB and to the bonding combination in the VB host, the charge density around the impurity is equilibrated in response to the perturbations in the equilibrium nuclear configuration and the intermediate band occupation.39,40 The equilibration follows a Le Chatelier principle through the modification of the contribution from the impurity to the IB and to the VB. Therefore, variations in the equilibrium configurations results in a small alteration of electronic density around the impurity and almost zero forces. In order to confirm the strong correlation and nuclear distortion effects on the GGA results, we will carry out additional analyses. Because the antiferromagnetic alignment is less stable than the ferromagnetic, we will focus our study on the ferromagnetic alignment. First, the atomic positions were allowed to relax. Without atomic relaxation, the local symmetry around the impurity is Td (four distances M-C = 1.888 Å). By relaxing the atomic positions, the local symmetry is lowered to C3v, with 3 distances similar and the others different. For Fe, Co, and Ni, the 3 distances similar are 2.01, 1.90, and 1.91 Å, and the other distance are 1.95, 2.05, and 2.07 Å, respectively. However, the IB splitting because of the Jahn−Teller deformation or Peierls distortion does not take place. In order to verify if the self-interaction in the partially full IB could split it, we have carried out the calculations using the GGA+U formalism described in refs 23 and 24, with U = 5 eV. This U value is larger than the U = 3 eV used for Fe−Ni-doped zinc chalcogenides in ref 24, which splits the IB. In addition, we have used two different occupation-number representations: the more common so-called on-site representation and the canonical Löwdin representation.23,24 The comparisons of these two different GGA+U calculations are shown in Figure 5. In all cases, the IB is not split. It could be the result of the dilution effect24 of the self-interaction. As well as, although we have used two different representations of the occupation numbers, the results are very similar. This partially full t+-IB allows additional photon absorption and emission channels. To corroborate it, the absorption coefficients have been obtained and split into interband transitions (Figure 6). They show an increase in light absorption below the host gap as a result of these additional absorption channels. The additional VB−IB and IB−CB transitions permit the absorption of lower energy photons than the host semiconductor. As a consequence, there is an increase in the number of carriers in the VB (electrons) and in the CB (holes). Therefore, the efficiency of the solar energy conversion could be increased with respect to the host semiconductor. M-doped silicon carbide could be used for novel optoelectronic devices. The IB−IB transitions do not significantly influence the operation of the solar cell because the external contacts are to the VB and to the CB. Therefore, the IB does not contribute to the carrier transport (electrons in the CB and holes in the VB) extracted by the contacts.

Figure 5. Comparison between the GGA+U projected DOS obtained using the on-site (“O” subindex) and the canonical Löwdin (“L” subindex) representation of the occupation numbers.23,24 The projected DOS are on the dt-M and p-M states of the M impurity and on the p-C states of the nearest neighbors for (a) M = Fe, (b) Co, and (c) Ni (x = 0.031). The Fermi energy has been chosen as zero energy in the figure.

4. CONCLUSIONS Using first-principles methods, we studied the optoelectronic properties of doped 3C-SiC with substitutional VIII-group atoms. The electronic structures for ferromagnetic and antiferromagnetic spin alignments have been analyzed for the MSi substitutions (M = Fe, Co, and Ni). In all cases, the band structure is characterized by a partially full t-IB in the gap with t symmetry, except for the minority spin component of the ferromagnetic spin alignments. In this case, the band structure is similar to the host semiconductor. The t-IB is made up of a combination of the dt-M states and the states with t symmetry of the first-nearest C neighbors. Therefore, the t electrons and the total magnetic moment of the cell are distributed among the M and the first-nearest neighboring states that make up the IB. 21952



Article

0.009. This material is available free of charge via the Internet at http://pubs.acs.org.

■ ■

AUTHOR INFORMATION

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS This work has been supported by the National Spanish projects Bibiana (PIB2010US-00096) and the European Commission through the funding of the project NGCPV (FP7-EU-JPN 283798), and by La Comunidad de Madrid through the funding of the project NUMANCIA-2 (ref. N: S-2009/ENE-1477).

■

Figure 6. Absorption coefficients for the transitions between the VB and the IB (VI+ in the figure), the VB and the CB (VC+ in the figure), the IB and the CB (IC+ in the figure), and inside the IB (II+ in the figure) for the majority spin component of the (a) FeSi, (b) CoSi, and (c) NiSi substitutions with x = 0.031.

Because of the characteristic of this t-IB, within the energy band gap and being partially full, we have analyzed the possible metal−insulator transition resulting from the nuclear distortion or strong correlation. For this end, we have used the GGA+U methodology with two different occupation-number representations. From the results, the t-IB is not split. It could be because of the dilution effect of the self-interaction and the selfregulation mechanism with respect to the perturbations in the equilibrium nuclear configuration and the intermediate band occupation. This partially full t+-IB allows additional photon transitions with respect to a single-gap host semiconductor. Therefore, these materials could be used for novel optoelectronic devices.

■

REFERENCES

(1) Matsunami, H. Current SiC Technology for Power Electronic Devices Beyond Si. Microelectron. Eng. 2006, 83, 2−4. (2) Patrick, L.; Choyke, W. Optical Absorption in n-Type Cubic SiC. J. Phys. Rev. 1969, 186, 775−777. (3) Choyke, W. J.; Patrick, L. Higher Absorption Edges in Cubic SiC. Phys. Rev. 1969, 187, 1041−1043. (4) Wiech, G. In Soft X-ray Band Spectra; Fabian, D. J., Ed.; Academic Press: New York, 1968. (5) Kobayashi, S. Calculation of the Energy Band Structure of the βSiC Crystal by the Orthogonalized Plane Wave Method. J. Phys. Soc. Jpn. 1958, 13, 261−268. (6) Grivickas, V.; Manolis, G.; Gulbinas, K.; Jarašiu̅nas, K.; Kato, M. Excess Carrier Recombination Lifetime of Bulk n-Type 3C-SiC. Appl. Phys. Lett. 2009, 95, 242110. (7) Zhe, C. F., Jian, H. Z., Eds. Silicon Carbide: Materials, Processing, and Devices; Taylor & Francis Books, Inc.: Boca Raton, FL, 2005. (8) Harris, G. L., Ed. Properties of Silicon Carbide; INSPEC (Institution of Electrical Engineers): London, U.K., 1995. (9) Woodbury, H. H.; Ludwig, G. W. Electron Spin Resonance Studies in SiC. Phys. Rev. 1961, 124, 1083−1089. (10) Hardeman, G. E. G. Electron and Nuclear Spin Resonance in ntype Silicon Carbide. J. Phys. Chem. Solids 1963, 24, 1223−1233. (11) Hagen, S. H.; van Kemenade, A. W. C. On the Role of Boron in the Luminescence of Silicon Carbide Doped with Nitrogen and Boron. Phys. Status Solidi A 1976, 33, 97−105. (12) Tajima, Y.; Kingery, W. D. Solid Solubility of Aluminum and Boron in Silicon Carbide. J. Am. Ceram. Soc. 1982, 65, C27. (13) Theodoropoulou, N.; Hebard, A.; Chu, S.; Overberg, M.; Abernathy, C.; Pearton, S.; Wilson, R.; Zavada, J.; Park, Y. Magnetic and Structural Properties of Fe, Ni, and Mn-Implanted SiC. J. Vac. Sci. Technol., A 2002, 20, 579. (14) Stromberg, F.; Keune, W.; Chen, X.; Bedanta, S.; Reuther, H.; Mücklich, A. The Origin of Ferromagnetism in 57Fe Ion-Implanted Semiconducting 6H-Polytype Silicon Carbide. J. Phys.: Condens. Matter 2006, 18, 9881−9900. (15) Luque, A.; Martí, A. Increasing the Efficiency of Ideal Solar Cells by Photon Transitions at Intermediate Levels. Phys. Rev. Lett. 1997, 78, 5014−5017. (16) Kohn, W.; Sham, L. J. Self-Consistent Equations Including Exchange and Correlation Effects. Phys. Rev. 1965, 140, A1133− A1138. (17) Private modification of the SIESTA code: Soler, J. M.; Artacho, E.; Gale, J. D.; García, A.; Junquera, J.; Ordejon, P.; Sánchez-Portal, D. The SIESTA Method for Ab Initio Order-N Materials Simulation. J. Phys.: Condens. Matter 2002, 14, 2745−2779 and references therein.. (18) Sankey, O. F.; Niklewski, D. J. Ab Initio Multicenter TightBinding Model for Molecular-Dynamics Simulations and Other Applications in Covalent Systems. Phys. Rev. B 1989, 40, 3979−3995. (19) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868. (20) Troullier, N.; Martins, J. L. Efficient Pseudopotentials for PlaneWave Calculations. Phys. Rev. B 1991, 43, 1993−2003.

ASSOCIATED CONTENT

S Supporting Information *

(i) Comparison between the projected DOS of the FM and AFM spin alignments, and between the structures with and without atomic relaxation; (ii) energy band structure around the Γ point for the (a) FeSi and (a) FeC substitutions with x = 21953



Article

(21) Kleinman, L.; Bylander, D. M. Efficacious Form for Model Pseudopotentials. Phys. Rev. Lett. 1982, 48, 1425−1428. (22) Anisimov, V. I.; Zaanen, J.; Andersen, O. K. Band Theory and Mott Insulators: Hubbard U Instead of Stoner. Phys. Rev. B 1991, 44, 943−954. (23) Tablero, C. Representations of the Occupation Number Matrix on the LDA/GGA + U Method. J. Phys.: Condens. Matter 2008, 20, 325205. (24) Tablero, C. Effects of the Orbital Self-Interaction in Both Strongly and Weakly Correlated Systems. J. Chem. Phys. 2009, 130, 054903. (25) O’Regan, D. D.; Payne, M. C.; Mostofi, A. A. Subspace Representations in ab Initio Methods for Strongly Correlated Systems. Phys. Rev. B 2011, 83, 245124. (26) Grisolía, M.; Rozier, P.; Benoit, M. Density Functional Theory Investigations of the Structural and Electronic Properties of Ag2V4O11. Phys. Rev. B 2011, 83, 165111. (27) Madelung, O., Ed. Landolt-Börnstein New Series III. In Zahlenwerte und Funktionen aus Naturwissenschaften und Technik; Springer: New York, 1987; Vol. 22a. (28) Bockstedte, M.; Mattausch, A.; Pankratov, O. Ab Initio Study of the Migration of Intrinsic Defects in 3C-SiC. Phys. Rev. B 2003, 68, 205201. (29) Persson, C.; Lindefelt, U. Relativistic Band Structure Calculation of Cubic and Hexagonal SiC Polytypes. J. Appl. Phys. 1997, 82, 5496. (30) Chang, K. J.; Froyen, S.; Cohen, M. L. Pressure Coefficients of Band Gaps in Semiconductors. Solid State Commun. 1984, 50, 105− 107. (31) Gubanov, V.; Boekema, C.; Fong, C. Electronic Structure of Cubic Silicon−Carbide Doped by 3d Magnetic Ions. Appl. Phys. Lett. 2001, 78, 216. (32) Miao, M.; Lambrecht, W. Magnetic Properties of Substitutional 3d Transition Metal Impurities in Silicon Carbide. Phys. Rev. B 2003, 68, 125204. (33) WeiHu, Z.; FuChun, Z.; ZhiYong, Z.; ShuYuan, L.; YanNing, Y. Electronic Structure and Magnetism of Fe-d®oped SiC Nanotubes. Sci. China 2010, 53, 1582−1589. (34) Kim, K. J.; Kim, Y.-W. Fe Doping and Magnetic Properties of Zincblende SiC Ceramics. J. Eur. Ceram. Soc. 2012, 32, 1149−1155. (35) Song, B.; Jian, J. K.; Li, H.; Lei, M.; Bao, H. Q.; Chen, X. L.; Wang, G. New Experimental Evidence for Origin of Ferromagnetism Ordering in Fe-Doped SiC. Phys. B 2008, 403, 2897−2901. (36) Li, D.; Jin, H.-B.; Cao, M.-S.; Chen, T.; Dou, Y.-K.; Wen, B. Production of Ni-Doped SiC Nanopowders and Their Dielectric Properties. J. Am. Ceram. Soc. 2011, 94, 1523−1527. (37) Fulde, P. Electron Correlation in Molecules and Solids; Solid-State Series; Springer: Berlin, Germany, 1993; Vol. 100. Madelung, O. Introduction to Solid-State-Theory; Springer Series in Solid State Sciences; Springer-Verlag: Berlin, Germany, 1996; Vol. 2. (38) Drabold, D. A.; Estreicher, S. Theory of Defects in Semiconductors; Springer: Berlin, Germany, 2007. (39) Tablero, C. Effects of the Impurity−Host Interactions on the Nonradiative Processes in ZnS:Cr. J. Appl. Phys. 2010, 108, 093114. (40) Tablero, C. Effects of the Impurity−Impurity and Impurity− Host Interactions on the Charge Density and the Related Processes. Phys. B 2009, 404, 4023−4028.

21954


Optoelectronic Application of the 3C-Silicon Carbide with

Recommend Documents