The Fe<sup>2+/3+</sup>donor level in CdTe

Szadkowski, A.

doi:10.1088/0953-8984/2/49/011

Cited by 21 publications

(11 citation statements)

References 11 publications

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“…We do not distinguish between the optical and the thermal ionization energy, because the lattice relaxation energy is very small for Fe in CdTe. 23 The presence of the second level is also seen in transport measurements. The conductivity of both CdTe:Fe and CdTe 0.9 Se 0.1 :Fe is of p type, due to residual acceptor impurities.…”

Section: Susceptibility Magnetization and Faraday Rotation In Twmentioning

confidence: 80%

Fe-based semimagnetic semiconductors with two anions

et al. 1996

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͑Cd 1Ϫx Fe x )͑Te 1Ϫy Se y ) crystals have been studied both theoretically and experimentally. In such a system, a part of Fe 2ϩ ions are located in crystal environments of a lowered symmetry. The energy level structure of these ions is substantially modified with respect to that of the Fe 2ϩ ion in one-anion ͑ternary͒ crystal. Regarding magnetic properties, the most essential modification occurs when an Fe 2ϩ ion is surrounded by three atoms of Te and one Se atom. Then, a doublet becomes a ground state of the magnetic ion, while, in the case of a ternary crystal, the ground state of an Fe 2ϩ ion is always a nonmagnetic singlet. In consequence, for two-anion systems, we observe a Curie-like paramagnetism instead of an otherwise revealed temperature independent (Tр10 K͒ Van Vleck paramagnetism. Although, in the present work, we are concerned mostly with ͑Cd 1Ϫx Fe x )͑Te 1Ϫy Se y ), a similar behavior is also observed for various crystals based on zinc and mercury. The results of our photoconductivity measurements indicate that the ground energetic state of an Fe 2ϩ ion can take several localizations in the band structure of the matrix crystal. A specific position depends on a configuration of nearest neighbors of an Fe 2ϩ ion, i.e., if it is surrounded by four Te, or three Te and one Se, etc. Concluding, we show that doped with Fe quaternary II-VI semimagnetic semiconductors demonstrate magnetic and optical properties essentially different from that of Fe doped ternary II-VI semimagnetic semiconductors.

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Section: Susceptibility Magnetization and Faraday Rotation In Twmentioning

confidence: 80%

Fe-based semimagnetic semiconductors with two anions

et al. 1996

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confidence: 79%

“…On the basis of the results of these measurements there has been recognized a state of iron, identified as the so-called deep donor and its ionization energy related to the transition Fe2+(d6 ) → Fe3+(d5 ) has been calculated to be 1.45 eV with respect to the bottom of the conduction band minimum (CBM). The existence of the donor-like state and its ionization energy value has been confirmed [6,8].Our reflectivity (RE), transmission and photoconductivity (PC) measurements procedure and experimental apparatus were described earlier [9]. The PC measurements were taken using modulated beam light (modulation frequency equal to 11 Hz) in the constant collecting electric field.…”

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confidence: 99%

Allocation and Properties of Iron States in Cd_1-xFe_xTe in Forbidden Gap Energy Range

1995

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The use of different experimental methods (reflectivity, absorption, photoconductivity and cathodoluminescence) allowed us to confirm the existence of the deep donor-like state of iron and present allocation and properties of the iron states in Cd1-yFexTe (0 < x < 0.05) at 300 K and 77 K in the forbidden gap energy range. It was concluded that the increase in width of the forbidden gap with the change of temperature from 300 K to 77 K leads mainly to the rise of the energy distance between the donor-like iron state 5 E and the bottom of the conduction band. PACS numbers: 78.20. Ci, 78.20.Jq, 78.60.Hk The semiconducting compound Cd1-xFexTe belongs to the family of diluted magnetic semiconductors [1,2]. The optical properties of this compound have been studied using absorption [3,4], reflectivity [5,6], and photo-EPR measurements [7]. On the basis of the results of these measurements there has been recognized a state of iron, identified as the so-called deep donor and its ionization energy related to the transition Fe2+(d6 ) → Fe3+(d5 ) has been calculated to be 1.45 eV with respect to the bottom of the conduction band minimum (CBM). The existence of the donor-like state and its ionization energy value has been confirmed [6,8].Our reflectivity (RE), transmission and photoconductivity (PC) measurements procedure and experimental apparatus were described earlier [9]. The PC measurements were taken using modulated beam light (modulation frequency equal to 11 Hz) in the constant collecting electric field. In the cathodoluminescence (CL) measurements the employed electron beam energy was 10 keV. Using the calibrated dependence of the lattice constant versus chemical composition presented in paper [6], the iron concentrations x were determined.Reviews of the E0 maxima energy positions obtained from the RE measurements and Epc PC signal as a function of iron concentration x at 300 K (RT) and

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“…The lattice relaxation energy related to iron centers in ZnSe:Fe was (rather carefully) estimated to be below 100 meV [5,6]. Even smaller value 20 meV was determined for CdTe:Fe [7].…”

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confidence: 99%

Hopping Conductivity in (Zn,Fe)Se Intentionally Doped with Ag

Zareba

Demianiuk²

1992

Acta Phys. Pol. A

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The transport phenomena in (Zn,Fe)Se were studied. In order to obtain iron centers in Fe 3 + charge state the crystals were doped by Ag what produces acceptors compensating Fee+ donors. The results are explained in terms of thermally activated jumping of charges between Fe 3+ and Fee + centers. The nature of activation energy is discussed. The polaron model seems to be not valid in our case. The Coulomb interaction between charged acceptors and "holes" on iron centers is considered as the origin of thermal activation of jumps. We suggest the deviation from random and mutually independent distributions of charged Ag acceptors and Fe 3 + ions resulting from the electrostatic interactions between them at high temperatures.PACS numbers: 71.55.Gs, 72.80.Ey More than 20 years ago studies on transport phenomena in phosphate glasses containing transition metal (TM) ions were carried out [1,2,3]. The thermally activated hopping of charges between TM ions in various charge states was proposed as the mechanism of conductivity.One may expect that a similar type of hopping could be observed in the II-VI semimagnetic semiconductors in which the levels of TM ions lie deep in the energy gap. We investigated the transport phenomena in the (Cd,Fe)Se crystals, where the Fe2+/3+ donor level lies about 600 meV above the top of the valence band. The results were interpreted in terms of "holes" (Fe in Fe3+ charge state) jumping to the nearest Fee+ centers [4]. A certain number of Fe 3 + ions is believed to result from the compensation caused by unidentified acception present in the crystals.Now we report the results of the studies of transport phenomena in (Zn,Fe)Se mixed crystals. In this material the Fe2 +/3 + donor level lies about 700 meV above the top of the valence band [5,6]. The as-grown crystals with iron content 0.6 at.% are semiinsulating. Their conductivity at 293 K is lower than 10 -1 0 S/cm. To produce Fe3+ centers necessary for hopping conductivity one has to dope the crystals with acceptors compensating iron donors. The Ag was chosen (749)

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The Fe^2+/3+donor level in CdTe

Cited by 21 publications

References 11 publications

Fe-based semimagnetic semiconductors with two anions

Fe-based semimagnetic semiconductors with two anions

Allocation and Properties of Iron States in Cd_1-xFe_xTe in Forbidden Gap Energy Range

Hopping Conductivity in (Zn,Fe)Se Intentionally Doped with Ag

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The Fe2+/3+donor level in CdTe

Cited by 21 publications

References 11 publications

Fe-based semimagnetic semiconductors with two anions

Fe-based semimagnetic semiconductors with two anions

Allocation and Properties of Iron States in Cd1-xFexTe in Forbidden Gap Energy Range

Hopping Conductivity in (Zn,Fe)Se Intentionally Doped with Ag

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The Fe^2+/3+donor level in CdTe

Allocation and Properties of Iron States in Cd_1-xFe_xTe in Forbidden Gap Energy Range