Defects In ZnSe Research Articles

Characterization of Quantum Emitters and Extended Defects in ZnSe via Multislice Electron Ptychography.

Characterization of Quantum Emitters and Extended Defects in ZnSe via Multislice Electron Ptychography.

Reduction of extrinsic defects in ZnSe:perovskite composites based solar devices

Reduction of extrinsic defects in ZnSe:perovskite composites based solar devices

On native point defects in ZnSe

Aiming at a fundamental understanding of the defect chemistry of pure ZnSe for optical and quantum applications, systematic density functional theory calculations with hybrid exchange-correlation functionals were performed to build an accurate database of native defects in ZnSe, including isolated defects and first nearest-neighbor defect–defect complexes. From the defect formation energies, zinc vacancy is found to be the most prevalent defect as the Fermi level approaches the conduction band edge, while zinc interstitial in the selenium tetrahedron and selenium vacancy become the most prevalent defects as the Fermi level approaches the valence band maximum. The divacancy complex, consisting of first nearest-neighboring zinc and selenium vacancies, is also found to have a favorable binding energy across the entire bandgap. Its formation energy is, however, always higher than either the isolated zinc or selenium vacancy, meaning it will never be the predominant defect in equilibrium. Finally, a point defect with extended spin coherence in Fluorine-implanted ZnSe was recently discovered, and it was found to exhibit a broad emission peak centered at 2.28 eV. The identity of this defect was determined to be either zinc vacancy or its associated complex according to the electron paramagnetic resonance measurements. Explicit simulations of the optical signatures of all zinc vacancy-related native defects were conducted here, showing that both zinc vacancy and divacancy are the most likely native defect contributors to that peak.

Optical marker of intrinsic point defects in ZnSe:Fe

We reveal a new luminescent center with a narrow emission line at 0.681 eV in iron-doped ZnSe at low temperatures. In addition to the main emission line, a satellite peak with a maximum at 0.683 eV and a vibronic band characteristic of intracenter transitions were clearly observed. The spatial distribution of the luminescence signal near 0.681 eV is correlated with the well-known (5T2 → 5E) iron-related luminescence profile, but the detected center was not observed in the samples obtained by iron doping in a zinc atmosphere. Our data indicate the presence of the emitting complex defect composed of a zinc vacancy and an iron ion. According to ab-initio calculations, the emission line at 0.681 eV can be tentatively assigned to an intracenter transition in the spin majority channel of the Fe ion attached to a Zn vacancy. The detected complex can be used as an “optical probe” for intrinsic point defects in crystalline ZnSe:Fe.

Combustion synthesis of ZnSe with strong red emission

A fast and furnace-free way is reported to synthesize ZnSe from self-sustained combustion reaction between Zn and Se. The synthesized ZnSe shows a zincblende structure and large particle size of >100μm, which can be reduced by two magnitude to 1.4μm by using NaCl as diluent. It is proposed that the added NaCl can lower the reaction temperature and diminish the interfacial area of ZnSe grains by a steric hindrance effect. The ZnSe samples show the characteristic band-edge absorption in visible region, and the band gap energy is estimated to be 2.43–2.58eV. Under an ultraviolet excitation, the ZnSe samples do not show the near-band-edge blue emission but exhibit strong red emission, which is likely related to the intrinsic point defects in ZnSe. Compared with previous studies, the ZnSe samples synthesized in this work show red emission peaks at even larger wavelength up to 730nm.

Simulating far infrared spectra of Zn1-xMnxSe/GaAs epifilms, MnSe/ZnSe superlattices and predicting impurity modes of N, P defects in Zn1-xMnxSe

A comprehensive lattice dynamical study is reported to emphasize the vibrational behavior of perfect/imperfect zinc-blende (zb) ZnSe, MnSe and Zn1−xMnxSe alloys. Low temperature far-infrared (FIR) reflectivity measurements performed on a series of molecular beam epitaxy grown Zn1−xMnxSe/GaAs (001) epilayers have a typical ‘intermediate-phonon-mode’ behavior. Besides perceiving ZnSe- and MnSe-like TO-phonon resonances, the study also revealed a weak Mn alloy-disorder mode below MnSe band. A classical effective-medium theory of multilayer optics is used to evaluate dielectric tensors of both epilayers and substrate for simulating reflectivity and transmission spectra of ultrathin epifilms and superlattices at near normal and/or oblique incidence. In the framework of a realistic rigid-ion model and exploiting an average t-matrix Greens function (ATM-GF) theory we appraised the vibrational properties of nitrogen and phosphorous doped Zn-Mn chalcogenides. Lattice relaxations around isolated NSe (PSe) defects in ZnSe and zb MnSe are evaluated by first principles bond-orbital model that helped construct perturbation models for simulating the localized vibrational modes (LVMs). Calculated shift of impurity modes for isotopic 14NSe (15NSe) defects in ZnSe offered a strong revelation of an inflexible defect–host interaction. By retaining force constant change parameter of 14NSe (15NSe) in heavily N-doped ZnSe, the ATM-GF theory predicted (a) three non-degenerate LVMs for the photoluminescence defect center V Se-Zn-14NSe (V Se-Zn-15NSe) of C s symmetry, and (b) six impurity modes for the second nearest-neighbor NSe-Zn-NSe pair defect of C 2v symmetry. From the range of simulated defect modes, we have ruled out the possibility of N-pairs and justified the presence of VSe-Zn-NSe complex centers – likely to be responsible for the observed large absorption bandwidth in highly N-doped ZnSe. High resolution measurements of FIR absorption and/or Raman scattering spectroscopy are needed to validate the accuracy of our theoretical conjectures.

Group-VII point defects in ZnSe

Zinc selenide (ZnSe) is a promising material for applications in quantum computing. Only recently, it was shown that fluorine-doped ZnSe may serve as a source for indistinguishable photons. We have studied both chlorine and fluorine point defects in ZnSe by means of first-principles density functional theory calculations. The incorporation of F or Cl, either isolated, pairwise, or in combination with Zn or Se vacancies, has been investigated thoroughly for a large variety of possible charge states. For the most important structures, computationally more demanding calculations, with a hybrid functional rather than the generalized gradient approximation for the treatment of electron exchange and correlation, have been carried out. This was found to have little effect on the energetical order of the defect, but considerably changes the absolute formation energies of the defects.

Slow mode degradation mechanism of ZnSe based white LEDs

AbstractThe cover picture is a photograph showing a row of ZnSe based white LEDs. In this issue's ‘Editor's Choice’ [1], the point defect induced degradation in these high quality diodes is investigated by electroluminescence, deep level transient spectroscopy, and isothermal capacitance transient spectroscopy investigations.The first author, Masahiro Adachi, is member of the Optoelectronics Laboratory at Tattori University, where he is working on microscopic defects in ZnSe based devices, defect induced degradation, and defect behaviour.The paper is an invited presentation from the II–VI '03 Conference held in Niagara Falls, New York, USA, 22–26 September 2003.The full Proceedings of the Eleventh International Conference on II–VI Compounds are published in physica status solidi (c) – conferences and critical reviews 1, No. 4 (March 2004) (ISBN 3‐527‐40510‐0).

Ab initio modeling of N–H, P–H and As–H defects in ZnSe

We have investigated the hydrogenation of group-V impurities (NSe, PSe and AsSe) in ZnSe by ab initio modeling. From the energetics, we conclude that among all sites considered for the H-atom, the bond centered location between Zn and the substitutional impurity, is the favorite. Metastable states by 0.6, 0.4 and 0.5eV were found for structures where H is antibonded to N, P and As, respectively. The calculated local vibrational mode frequencies for N–H and As–H agree well with the available experimental data, whereas a 2331cm−1 stretch and a 392cm−1 wag mode frequencies are anticipated for P–H.

Instability of Cl-Related Deep Defects in ZnSe

We have studied the instability of Cl-related deep defects in ZnSe by means of far-infrared magnetooptical absorption measurements. Zeeman absorption corresponding to 1s–2p+ transition of electrons bound to Cl donors has been observed under photoexcitation. The absorption intensity increases with the lapse in time after photoexcitation, and saturates in approximately 1 h. These results suggest the presence of deep states in the midgap, which are evidently associated with its photoinduced transformation.

Induced Defects in ZnSe and ZnTe by Electron and Proton Irradiation and Defect-Annealing Behaviour

In this study we discuss the microstructural changes after electron and proton irradiation and the thermal evolution of the radiation induced defects during isochronal annealing in ZnSe and ZnTe. The nominally undoped samples were irradiated either with 1 MeV or 2 MeV electrons or with 3 MeV protons. The investigation was performed with positron lifetime and Doppler-broadening measurements.

Native and impurity defects in ZnSe:In single crystals prepared by free growth

The optical absorption and photoluminescence spectra and the Hall effect were studied in ZnSe:In single crystals. The presence of electrically active InZn+ donor centers responsible for the impurity absorption and electrical conduction of crystals is established. It is shown that the conduction compensation in the ZnSe:In crystals is effected by cationic vacancies. The InZn+ donors and cationic vacancies form associative defects responsible for long-wavelength ZnSe:In luminescence. A high crystal conductivity (∼5 Ω−1 cm−1) is achieved as a result of ZnSe:In annealing in the zinc melt, which results in the extraction of cationic vacancies. The electron mobility in high-conductivity crystals is limited by scattering at the LO phonons and macrodefects formed due to the reduction of In solubility in crystals by their annealing in zinc.

Predicted lattice relaxation around point defects in zinc selenide

There is great interest in altering the electronic and consequent optical properties of wide-band-gap semiconductors through the use of selected additives (dopants). These effects depend on the way in which the impurity enters the lattice structure, and the resulting possible lattice relaxation effects and their repercussions. There have been several calculations for the point defects in ZnSe based on pseudopotential approaches, with some differences in results among these; and, in the case of nitrogen substitution for the selenium, there is a difference with experiment as to the expected size of relaxation effects around the defect. Thus it is useful to have calculations by a quite different technique. For that reason, as benchmark calculations, we have studied lattice relaxation around Zn and Se vacancies, and around N-for-Se substitution sites in ZnSe $[{\mathrm{V}}_{\mathrm{Se}},$ $({\mathrm{V}}_{\mathrm{Se}}{)}^{++},$ ${\mathrm{V}}_{\mathrm{Zn}},$ $({\mathrm{V}}_{\mathrm{Zn}}{)}^{\ensuremath{-}\ensuremath{-}},$ ${\mathrm{N}}_{\mathrm{Se}},$ and $({\mathrm{N}}_{\mathrm{Se}}{)}^{\ensuremath{-}}],$ using a full-potential, linear combination of muffin-tin orbitals total energy calculation including an atomic force routine. We have obtained results for the lattice response of ZnSe in various configurations, and discuss these in comparison to the pseudopotential results and experiment. For the case of nitrogen substitution for selenium, we also present an independent experimental verification of previously reported results for the unusually large lattice relaxation surrounding this defect.

Thermal stability of Li-related 1D defects in ZnSe:Li/GaAs grown by MBE

Curved streak patterns are clearly observed in the azimuth of [1 0 0] when the substrate temperature is heated up to 600°C, suggesting that the one-dimensional Li chains are stable. The growth rates of non-doped ZnSe on Li-doped ZnSe are found to be about 1/2 of that of non-doped ZnSe grown on GaAs. Even when no Li is supplied, the RHEED exhibits clear curved streak patterns. The results indicate that Li atoms segregate onto the topmost surface during the MBE growth, because of high diffusivity of Li, resulting in the formation of 1D array.

Modeling of Chlorine Related Defects and Complexes in ZnMgSe

ABSTRACTWe have used the ab-initio full potential LMTO method to model native defects and chlorine-impurity-related defects in ZnSe and ZnxMg1−xSe. Our results show that there is a strong tendency for formation of a defect complex between a chlorine impurity at the Se site and a vacancy at the neighboring Zn site. The formation energies of this complex and other chlorine related defects decrease in the presence of magnesium. However, the maximum achievable electron concentration in the presence of magnesium is lower because of the increase in the band gap.

Ab initio energy calculation of nitrogen-related defects in ZnSe

We present results of optical degradation experiments on II–VI laser diodes. The illumination is done with a microfocus to allow the degradation of stacking-fault-free regions. A degradation is only observed if the excited region (in our case the waveguide) is doped with nitrogen. Parallel to the decrease of the quantum-well luminescence, we observe the increase of a deep luminescence signal from the waveguide region. Under reverse bias the degradation rate is decreased. Based on density functional calculations, this behaviour can be explained by a deplacement of the nitrogen from the substitutional to the interstitial site. The resulting complex of a selenium vacancy and the nitrogen interstitial is considerably more stable than the nitrogen acceptor.

Characterization of etch pits and correlated defects in ZnSe/(001)GaAs

Microscopy Research and TechniqueVolume 43, Issue 6 p. 518-519 Characterization of etch pits and correlated defects in ZnSe/(001)GaAs Shigeyasu Tanaka, Corresponding Author Shigeyasu Tanaka Department of Electronics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, JapanDept. of Electronics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.Search for more papers by this authorTomohiro Goto, Tomohiro Goto Department of Electronics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, JapanSearch for more papers by this authorMichio Hibino, Michio Hibino Center for Integrated Research in Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, JapanSearch for more papers by this author Shigeyasu Tanaka, Corresponding Author Shigeyasu Tanaka Department of Electronics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, JapanDept. of Electronics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.Search for more papers by this authorTomohiro Goto, Tomohiro Goto Department of Electronics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, JapanSearch for more papers by this authorMichio Hibino, Michio Hibino Center for Integrated Research in Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, JapanSearch for more papers by this author First published: 29 December 1998 https://doi.org/10.1002/(SICI)1097-0029(19981215)43:6<518::AID-JEMT5>3.0.CO;2-0AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume43, Issue615 December 1998Pages 518-519 RelatedInformation

Characterization of etch pits and correlated defects in ZnSe/(001)GaAs.

Characterization of etch pits and correlated defects in ZnSe/(001)GaAs.

Effect of Plastic Deformation on the Luminescence of ZnSe Crystals

The electronic recombination properties of defects in ZnSe is a subject of interest related to the application of this material in optoelectronic devices operating in the blue-green range. In this work the influence of defects, in particular the deformation induced defects, on the luminescence of bulk ZnSe single crystals has been investigatd by cathodoluminescence in the SEM. The crystals were compressed along [100] direction wih plastic strains of 3% and 6.4% respectively. Deformation has been found to cause a reduction of the total CL intensity of the sample. CL images of deformed samples reveal dark slip bands. The CL spectrum of an undeformed crystal at 85K shows the near band edge emission at 2.8eV and a broad band peaked at 2.2eV with a shoulder at about 2eV. Deformation at the low strain causes only slight spectral changes while in the heavily deformed crystal a strong relative enhancement of the deep level band in the range 2-2.2eV is observed. The relation of these spectral changes with the deformation induced defects is discussed.

Reduction of the extended defect density in molecular beam epitaxy grown ZnSe based II-VI heterostructures by the use of a BeTe buffer layer

The reduction of extended defects in ZnSe based II-VI heterostructures grown by molecular beam epitaxy on (001) GaAs is reported, using BeTe buffer layers as a novel approach. After defect selective chemical etching three different types of etch pits could be observed by optical microscopy. By the application of a thin BeTe buffer layer the density of paired Frank type stacking faults could be strongly reduced to values below 103 cm−2. The role of Se in the background pressure for the defect nucleation at the II-VI/GaAs interface is significant. It has been found that BeTe can form a smooth interface to GaAs and ZnSe which is reflected in high resolution x-ray diffraction data.