Comparison of magneto-optical properties of various excitonic complexes in CdTe and CdSe self-assembled quantum dots
J. Kobak, T. Smoleński, M. Goryca, J.-G. Rousset, W. Pacuski, A. Bogucki, K. Oreszczuk, P. Kossacki, M. Nawrocki, A. Golnik, J. Płachta, P. Wojnar, C. Kruse, D. Hommel, M. Potemski, T. Kazimierczuk
aa r X i v : . [ c ond - m a t . m e s - h a ll ] F e b Comparison of magneto-optical properties of various excitonic complexes in CdTe and CdSeself-assembled quantum dots
J. Kobak, ∗ T. Smole´nski, M. Goryca, J.-G. Rousset, W. Pacuski, A. Bogucki, K. Oreszczuk, P. Kossacki, M. Nawrocki, A. Golnik, J. Płachta, P. Wojnar, C. Kruse, D. Hommel, M. Potemski, and T. Kazimierczuk Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 00-093 Warsaw, Poland Institute of Physics, Polish Academy of Sciences, al. Lotnik´ow 32/64, 02-688 Warsaw, Poland Institute of Solid State Physics, Semiconductor Epitaxy, University of Bremen, PO Box 330 440, D-28334 Bremen, Germany Laboratoire National des Champs Magn´etiques Intenses CNRS-UGA-UPS-INSA-EMFL, 30942 Grenoble, France
We present a comparative study of two self-assembled quantum dot (QD) systems based on II-VI compounds:CdTe/ZnTe and CdSe/ZnSe. Using magneto-optical techniques we investigated a large population of individ-ual QDs. The systematic photoluminescence studies of emission lines related to the recombination of neutralexciton X, biexciton XX, and singly charged excitons (X + , X − ) allowed us to determine average parametersdescribing CdTe QDs (CdSe QDs): X–XX transition energy difference meV ( meV); fine-structure split-ting δ = 0 . meV ( δ = 0 . meV); g -factor g = 2 . ( g = 1 . ); diamagnetic shift γ = 2 . µ eV / T ( γ = 1 . µ eV / T ). We find also statistically significant correlations between various parameters describinginternal structure of excitonic complexes. I. INTRODUCTION
Epitaxial quantum dots (QDs) are renowned for their di-versity — in a single sample one can find QDs with differ-ent values of emission energy, anisotropy-induced exchangesplitting, effective Land´e factor, diamagnetic shift, and otherparameters. It can be an advantage, if a single QD with partic-ular properties (e.g., zero anisotropy splitting ) is required.On the other hand, such a diversity is an obstacle on the wayto determine the typical behavior of QDs in a given materialsystem.Precise determination of a typical QD parameters re-quires averaging over many individual dots. In case ofsome characteristics, such as emission energy or g -factor,it is possible to simply measure the response of the wholeQD ensemble, e.g., in photoluminescence (PL) or time-resolved Faraday rotation experiments, respectively. How-ever, more detailed characteristics such as anisotropic fine-structure splitting (FSS) can be studied directly only on asingle-dot level and thus a significant number of individualdots need to be analyzed in order to draw robust conclusionsabout the average value.In this work we present results of systematic comparisonbetween the two popular II-VI self-assembled QD systems:CdTe/ZnTe and CdSe/ZnSe. We particularly focus on differ-ences between excitons of various charge states: their bindingenergy, g -factor and diamagnetic shift. These quantities havebeen already measured for single quantum dots , but havenot been analyzed in terms of variation across the QD popula-tion. II. SAMPLES AND EXPERIMENTAL SETUP
We studied 3 structures with CdSe QDs in ZnSe barriersand 4 structures with CdTe QDs in ZnTe barriers. Sampleswere fabricated in three different laboratories (affiliations 1,2, and 3). The growth of the structures was performed bymolecular beam epitaxy (MBE) on GaAs substrates. In most cases the reorganization of the QDs was induced by a well-established amorphous Te or Se desorption method forwhich the growth temperature was varied just after deposi-tion of the QD formation layer. For the two selenide samplesthe cap layer was deposited directly on the QDs layer with-out changing the substrate temperature. In order to reduceQDs density in selenide samples we applied additional lowlevel delta-doping with transition metal ions . However,in this work we include only results obtained for individualQDs, which do not contain magnetic ions inside.The studied samples were placed inside a magneto-opticalbath cryostat with magnetic field of up to 10 T. The measure-ments were performed at the temperature of about 1.5 K usinga reflective type microscope, which focuses the laser beamto a 0.5 µ m diameter spot. This allowed us to study opticalproperties of well-resolved emission lines of single QDs inhigh magnetic fields with a polarization resolution. Comple-mentary magneto-optical studies were performed in GrenobleHigh Magnetic Field Laboratory, where a helium-bath cryo-stat (4.2 K) with a sample was placed inside a 20 MW resistivemagnet producing magnetic field of up to 28 T. III. RESULTS
In order to present statistically significant data we have in-vestigated over 160 individual QDs. For each analyzed QDwe studied emission lines originating from the recombinationof the neutral exciton X, the biexciton XX, and the charged ex-citons (X + , X − ). Identification of such lines has been alreadydiscussed in detail elsewhere. Typically it includes theanalysis of linear polarization of emission and the dependenceof the PL intensity on the excitation power. Based on the PLspectra measured in magnetic field of 0-10 T we extracted pa-rameters describing each of the studied excitonic transitions:their relative emission energies, anisotropy-induced exchangesplittings, effective Land´e g -factors, and diamagnetic shift co-efficients γ . CdSe / ZnSeCdTe / ZnTe X-X+EX-EXX (meV)X- X+
E X - E li ne ( m e V ) Photon Energy (meV)Photon Energy (meV)(c)(b)(a) CdSe / ZnSe QDCdTe / ZnTe QDX2- X-X- X+ X+XX XX XX P L i n t en s i t y P L i n t en s i t y FIG. 1. (Color online) Relative emission energy of various excitoniccomplexes in QDs. (a,b) Photoluminescence spectra of CdTe/ZnTeand CdSe/ZnSe QDs, respectively. The QDs show typical anisotropyproperties: the emission lines of the neutral exciton (X) and biexciton(XX) exhibit opposite linear polarizations, while the lines related tothe trions (X + , X − ) are not linearly polarized. (c) Energy differencebetween the neutral exciton line and the charged exciton lines plottedversus the energy difference between the neutral exciton line and thebiexciton line for CdTe/ZnTe (red and blue symbols) and CdSe/ZnSe(black and green symbols) QDs. Solid lines mark the linear fits ( y = ax ) with proportionality constants equal to a CdTeX + = 0 . , a CdTeX − =0 . , a CdSeX + = 0 . , a CdSeX − = 0 . (compare with Refs. 25 and 27).Dashed line corresponding to y = x is drawn for the reference. A. Relative emission energy of X, XX, X + , and X − The energy of the emission lines related to particular QDstrongly depends, e.g., on the growth procedure and the QDsize , but in this work we focus rather on the structure of aPL spectrum of a single QD. Figs 1(a) and 1(b) present PLspectra of a single CdSe/ZnSe and CdTe/ZnTe QD. Due to the Coulomb interaction, emission lines of different excitoniccomplexes are shifted from the basic neutral exciton X. Rel-ative energies of different lines may vary depending on theQD size, shape and composition. However, in accordancewith Ref. 25 and 27 we find that for telluride QDs the dis-tances between the emission lines vary almost proportionallyto each other (Fig. 1(c)). Consequently, the emission patternstays roughly the same, except for some variation of the hor-izontal scale. Such an effect significantly simplifies identifi-cation of the PL lines originating from a single CdTe/ZnTeQD in the experiment. As shown in Fig. 1(c), the situation inthe selenide system is different. Distances between the X + ,X − and X lines in case of the selenide QDs cannot be consid-ered proportional to the X–XX distance. Although there ex-ists some positive correlation between the X–X − , X–X + dis-tances and the X–XX distance (Pearson’s correlation coeffi-cients r X − = 0 . and r X + = 0 . , compared to r X − = 0 . and r X + = 0 . found for the tellurides), their relationshipdoes not correspond to a simple proportionality (see Fig. 1(c)).We note that while all studied CdTe QDs exhibited the samesequence of excitonic transitions in the PL spectrum, for theselenide QDs the negatively charged exciton line can be situ-ated either on higher or on lower energetic side of the neutralbiexciton line.Another important difference between the two material sys-tems is the average value of the relative X–XX transition en-ergy distance. In the case of telluride QDs such an averageenergy distance is equal to about . meV, while for the se-lenide QDs the obtained average value is about twice as highand yields . meV. B. Anisotropic exchange splitting of X and XX
By means of the PL measurements performed with a polar-ization resolution of detection we analyzed the fine-structureof the X and XX states for CdTe and CdSe QDs (Fig. 2). Inthe case of both excitonic complexes the zero-field emissioncontains two lines split by the energy related to the anisotropicpart of the exchange interaction between the electron and theheavy hole . Such emission lines can be seen separately intwo perpendicular linear polarizations of the detection. As ex-pected, for each QD we observed the same value of anisotropysplitting of X and XX, but opposite ordering of the fine-structure-split components for both complexes. This is dueto the fact that X is the final state of the XX transition. In theexperiment, for each studied dot we collected the PL spectraas a function of linear polarization angle of detection. Sucha measurement provides information not only about the valueof the fine-structure splitting ( δ ) but also about the in-planeanisotropy axis of each QD. Coherently with the previous re-ports on II-VI QDs we do not observe any correlation be-tween the in-plane anisotropy parameters (splitting and direc-tion) and both the transition energy and the biexciton rela-tive energy. For the telluride QDs the average value of thefine-structure splitting δ is about . meV, whereas for theselenide QDs we found a few times higher average value of δ = 0 . meV. (d)(c) (b)(a) CdTe / ZnTe QDsCdSe / ZnSe QDsCdTe / ZnTe QDCdSe / ZnSe QD N u m be r o f Q D s Anisotropy splitting (meV)Photon Energy (meV) P L i n t en s i t y N u m be r o f Q D s Anisotropy splitting (meV)Photon Energy (meV) P L i n t en s i t y FIG. 2. (Color online) Anisotropy splitting of the neutral exciton. (a,c) Example PL spectra of the bright neutral exciton (X) in CdSe/ZnSeand CdTe/ZnTe QD, respectively. The spectra were detected in twoorthogonal linear polarizations, the orientations of which correspondto the principal axes of the QD anisotropy. (b, d) Distribution ofthe X anisotropy splitting in various CdSe/ZnSe and CdTe/ZnTe QD,respectively.
C. Zeeman effect and diamagnetic shift
The energy spectrum of the QD can be manipulated by ex-ternal magnetic field. Two main effects occurring upon appli-cation of the magnetic field are a linear splitting of the statesdepending on the spin projection (Zeeman effect) and aquadratic energy shift due to a finite spatial extension of theexciton wave function (diamagnetic shift) . The strength ofthese effects is parametrized with the excitonic g -factor andthe diamagnetic field coefficient γ .In our experiments we studied these parameters in the Fara-day geometry with the magnetic field applied along the growthaxis of the QDs. As expected, the transitions of all consideredexcitonic complexes exhibit a common field-induced splittingpattern comprising of two lines separated by the energy of p ∆ + ( gµ B B ) , where g is the g -factor, while ∆ corre-sponds to the zero-field splitting (equal to δ for the neutralcomplexes and 0 in case of the trions). In order to take intoaccount the change of the mean emission energy (originatingfrom the diamagnetic shift), we fitted both Zeeman branchesof a given transitions with a quadratic formulas of the form E ( B ) = E ± p ∆ + ( gµ B B ) + γB , where + ( − ) signcorresponds to the higher (lower) energy line.The results of the fitting are presented in Fig. 3. The av-erage g -factor of the CdTe QDs ( g = 2 . ) was found tobe slightly larger than the average g -factor of the CdSe QDs( g = 1 . ). More significant differences we obtained bystudying the diamagnetic shift, which was found to be approx-imately two times higher for the telluride QDs ( . µ eV / T )compared to the selenide ones ( . µ eV / T ), as shown inFigs 3(c,f). These values can be expressed using a more com-prehensive quantity of the spatial extension of the excitonic wave function according to a relation γ = e m h r i , (1)where m is the in-plane reduced mass of the exciton. Oneshould note that this expression is strictly valid only for thesystems with translational symmetry in the plane perpendic-ular to the magnetic field (i.e., in bulk or quantum wells) .By applying this formula also to the case of QDs we ob-tained the values of the spatial extension of the excitonic wavefunction in normal configuration for CdSe and CdTe QDs as p h r i = 2 . nm and . nm, respectively. Such values stay ina good agreement with the material trends. More specifically,dielectric constant is smaller for the selenides , which leadsto a stronger electron-hole interaction. As a consequence, theCdSe QDs exhibit stronger exciton binding and smaller radiusof the excitonic wave function. The obtained values can bealso compared with the bulk exciton radii, which yield 5.6 nmfor CdSe and 7.5 nm for CdTe . In each system the confine-ment in the QD potential reduces the extension of the excitonwavefunction, yet only up to about 60%.The most surprising findings are obtained from the cor-relations between the effective Land´e g -factors determinedfor different excitonic complexes. Since each of the studiedlines is related to the recombination of an s-shell hole with ans-shell electron, all these transitions for a given QD are ex-pected to exhibit the same excitonic g -factor. Nevertheless, Y.L´eger et al. reported about a CdTe QD with different valuesof g -factors for various excitonic complexes. Our measure-ments corroborate this claim and demonstrate the existence ofa systematic deviation between the g -factors of X, X + , andX − transitions in the whole population of the QDs. Such asystematic difference was found in both systems, but with op-posite sign, as seen in Fig. 4.In the case of CdTe QDs we observed with perfect regu-larity that the g -factor of the neutral exciton is greater thanthe g -factor of the X − and smaller than the g -factor of theX + . The average difference between the g -factor values cor-responding to X + and X was equal to . , while the dif-ference between the g -factor of X − and X was about threetimes smaller ( . ). For the selenide QDs we observed op-posite sign of this effect: greater values of the g -factors forX − states and smaller for X + stats in comparison to X Land´efactor. However, due to significantly lower mean values ofthe g -factor differences and fluctuations of the g-factor dis-tribution we found a few exceptions from such an ordering.With respect to the X g -factor, Land´e factor of X − state wason average larger by . , while the g -factor of X + state wassmaller by about . . We interpret the observed differencesbetween the g -factor values for various excitonic complexesas resulting from significant modification of the carrier wavefunction imposed by the presence of the other carriers in thedot. We note that for both QDs systems the Land´e factors of Xand XX were equal for all dots within our experimental uncer-tainty. Such a relation is expected, since the singlet nature ofthe biexciton state implies that the Zeeman effect of the XXtransition originates solely from the final state, i.e., the neutral (d) (c)(b)(a) CdTe / ZnTe QDsCdSe / ZnSe QDs N u m be r o f Q D s G-factor (b) (c)(e) (f)QDCdSeQDCdTe N u m be r o f Q D s G-factor 0 2 4 6 80246810
CdTe / ZnTe QDsCdSe / ZnSe QDs N u m be r o f Q D s Diamagnetic shift ( eV/T )0 2 4 6 80246810 N u m be r o f Q D s Diamagnetic shift ( eV/T )Photon Energy (meV) M agne t i c F i e l d ( T ) Photon Energy (meV) M agne t i c F i e l d ( T ) FIG. 3. (Color online) Magneto-spectroscopy of the neutral exciton state (X) together with the distribution of excitonic g -factors and dia-magnetic shift coefficients among the studied dots. (a, d) The evolution of X emission line in external magnetic field applied in the Faradaygeometry. (b, e) Histograms of the Land´e g -factor values for various CdSe/ZnSe and CdTe/ZnTe QDs. (c, f) Histograms of diamagnetic shiftcoefficients for various CdSe/ZnSe and CdTe/ZnTe QDs. XXX - X + XXX - X + XXX - X + g-factor of X g - f a c t o r o f X + , X - , and XX g-factor of X g - f a c t o r o f X + , X - , and XX (d)(c)(a) (b)(a) CdTe QDsCdSe QDsCdTe QDsCdSe QDs Diamagnetic shift of X ( eV/T ) D i a m agne t i c s h i ft o f X + , X - , and XX XXX - X + Diamagnetic shift of X ( eV/T ) o f X + , X - , and XX D i a m agne t i c s h i ft FIG. 4. (Color online) Statistic parameters describing the magneto-optical characteristics of CdSe/ZnSe (a, b) and CdTe/ZnTe (c, d) QDsin the Faraday configuration: (a, c) Correlation of the Land´e g -factorsfor different excitonic complexes. (b, d) Correlation of diamagneticshift coefficients for different excitonic complexes. exciton state. Average differences of the g -factors of X andXX states were equal . and . for telluride and se-lenides QDs, respectively, which is indeed much smaller thandifferences between the charged excitons g -factors discussedearlier.In analogy to the study of the Land´e factors, we also inves-tigated correlations between diamagnetic shift constants forvarious excitonic complexes. For both QDs systems we do notobserve any systematic differences, except that for selenideQDs the diamagnetic shift of the X tended to be slightly largerthan for the other complexes. However, in the case of CdTe QDs we obtained similar values of the diamagnetic shifts co-efficients for various excitons in a given dot. IV. SUMMARY
By means of magneto-optical techniques we have stud-ied and compared the two systems of self-organized QDs:CdTe/ZnTe and CdSe/ZnSe QDs. We investigated over 160randomly selected individual QDs. To reduce the influence ofthe effects related to the growth technique and specific sample,we examined 7 structures fabricated in 3 laboratories. Basedon such statistical approach we determined the key param-eters describing magneto-optical properties of the excitoniccomplexes in CdTe/ZnTe and CdSe/ZnSe QDs. The averagevalues of the characteristic parameters describing the studiedQDs are summarized in Table I.Typical spectra of individual CdTe QD contain severalemission lines that form a characteristic pattern. For most ofthe studied CdTe dots the energy distances between the emis-sion lines related to various charged states vary proportionally
CdSe/ZnSe QDs CdTe/ZnTe QDs E X − E XX (meV) . ± . . ± . δ (meV) . ± .
21 0 . ± . g X (number) . ± .
21 2 . ± . g X + − g X (number) − . ± .
07 0 . ± . g X − − g X (number) . ± . − . ± . γ X ( µ eV / T ) . ± . . ± . TABLE I. Average values of the parameters describing CdTe andCdSe QDs. The symbols are introduced and explained in the text.Uncertainties were calculated as a standard deviation of the deter-mined parameters. to the energy distance of X and XX. In the case of selenideQDs we observed much weaker correlation of the relativeenergy positions of the emission lines. Furthermore, the se-quence of the emission lines is not conserved for all dots, i.e.,the energy of X − emission line can be either higher and lowerthan the energy of XX line. Analysis of the magnetic fielddependence of the emission spectra revealed an unexpectedeffect of the systematic difference between the g -factors ofvarious excitonic complexes, especially for the CdTe system.The comparison between the parameters determined forCdTe and CdSe QDs is consistent with the general mate-rial trends. In particular, the smaller dielectric constant ofselenides leads to a stronger Coulomb interaction betweenthe carriers, which is reflected by the higher bulk exciton bind-ing energy. Similarly, the selenide QDs exhibit larger en-ergetic distance between the exciton and the biexciton emis-sion lines, larger anisotropic part of the electron-hole ex-change interaction and tighter binding of the carriers in theexcitonic complexes evidenced by a smaller value of the dia- magnetic shift coefficient.
ACKNOWLEDGMENTS
This work was partially supported by the Polish NationalScience Centre under decisions DEC-2012/05/N/ST3/03209,DEC-2013/09/B/ST3/02603, DEC-2011/02/A/ST3/00131,and by Polish Ministry of Science and Higher Education inyears 2012 − ◦ IP2014 034573). One of us (T.S.) wassupported by the Foundation for Polish Science through theSTART programme. The research leading to these resultshas received funding from the European Union SeventhFramework Programme (FP7/2007-2013) under grant agree-ment N ◦ ∗ [email protected] R. J. Young, R. M. Stevenson, A. J. Shields, P. Atkinson,K. Cooper, D. A. Ritchie, K. M. Groom, A. I. Tartakovskii, andM. S. Skolnick,
Inversion of exciton level splitting in quantumdots , Phys. Rev. B , 113305 (2005). R. M. Stevenson, R. J. Young, P. Atkinson, K. Cooper, D. A.Ritchie, and A. J. Shields,
A semiconductor source of triggeredentangled photon pairs , Nature , 179 (2006). S. K. Zhang, T. Myint, W. B. Wang, B. B. Das, N. Perez-Paz,H. Lu, M. C. Tamargo, A. Shen, and R. R. Alfano,
Optical studyof strongly coupled CdSe quantum dots , J. Vac. Sci. Technol. B , C3D17 (2010). M. Syperek, D. R. Yakovlev, I. A. Yugova, J. Misiewicz, I. V.Sedova, S. V. Sorokin, A. A. Toropov, S. V. Ivanov, andM. Bayer,
Long-lived electron spin coherence in CdSe/Zn(S,Se)self-assembled quantum dots , Phys. Rev. B , 085304 (2011). I. I. Reshina, S. V. Ivanov, and A. A. Toropov,
Magneto-optical studies of ensembles of semimagnetic self-organizedCd(Mn)Se/Zn(Mn)Se quantum dots , Phys. Rev. B , 155302(2012). M. T. Man and H. S. Lee,
Discrete states and carrier-phononscattering in quantum dot population dynamics , Sci. Rep. , 8267(2015). S. N. Walck and T. L. Reinecke,
Exciton diamagnetic shift in semi-conductor nanostructures , Phys. Rev. B , 9088 (1998). V. D. Kulakovskii, G. Bacher, R. Weigand, T. K¨ummell,A. Forchel, E. Borovitskaya, K. Leonardi, and D. Hommel,
FineStructure of Biexciton Emission in Symmetric and AsymmetricCdSe/ZnSe Single Quantum Dots , Phys. Rev. Lett. , 1780(1999). A. Hundt, T. Flissikowski, M. Lowisch, M. Rabe, and F. Hen-neberger,
Excitation Spectrum, Relaxation and Coherence of Sin-gle Self-Assembled CdSe Quantum Dots , Phys. Stat. Sol. B ,159 (2001). M. Bayer, G. Ortner, O. Stern, A. Kuther, A. A. Gorbunov,A. Forchel, P. Hawrylak, S. Fafard, K. Hinzer, T. L. Rei-necke, S. N. Walck, J. P. Reithmaier, F. Klopf, and F. Sch¨afer,
Fine structure of neutral and charged excitons in self-assembledIn(Ga)As/(Al)GaAs quantum dots , Phys. Rev. B , 195315 (2002). L. Besombes, K. Kheng, L. Marsal, and H. Mariette,
Few-particleeffects in single CdTe quantum dots , Phys. Rev. B , 121314(2002). J. J. Finley, D. J. Mowbray, M. S. Skolnick, A. D. Ashmore,C. Baker, A. F. G. Monte, and M. Hopkinson,
Fine structure ofcharged and neutral excitons in InAs-Al . Ga . As quantum dots ,Phys. Rev. B , 153316 (2002). C. Schulhauser, A. H¨ogele, R. J. Warburton, A. O. Govorov,W. Schoenfeld, J. M. Garcia, P. M. Petroff, and K. Karrai,
Mag-netic properties of charged excitons in self-assembled quantumdots , Phys. Stat. Sol. (b) , 293 (2003). I. A. Akimov, K. V. Kavokin, A. Hundt, and F. Henneberger,
Electron-hole exchange interaction in a negatively charged quan-tum dot , Phys. Rev. B , 075326 (2005). Y. L´eger, L. Besombes, L. Maingault, and H. Mariette,
Valence-band mixing in neutral, charged, and Mn-doped self-assembledquantum dots , Phys. Rev. B , 045331 (2007). D. Y. Oberli, M. Byszewski, B. Chalupar, E. Pelucchi, A. Rudra,and E. Kapon,
Coulomb correlations of charged excitons in semi-conductor quantum dots , Phys. Rev. B , 165312 (2009). K. P. Hewaparakrama, S. Mackowski, H. E. Jackson, L. M. Smith,W. Heiss, and G. Karczewski,
Tuning spin properties of excitonsin single CdTe quantum dots by annealing , Nanotechnology ,125706 (2008). F. Tinjod, B. Gilles, S. Moehl, K. Kheng, and H. Mariette,
II–VI quantum dot formation induced by surface energy change of astrained layer , Appl. Phys. Lett. , 4340 (2003). P. Wojnar, C. Bougerol, E. Bellet-Amalric, L. Besombes, H. Ma-riette, and H. Boukari,
Towards vertical coupling of CdTe/ZnTequantum dots formed by a high temperature tellurium inducedprocess , J. Cryst. Growth , 28 (2011). J. Kobak, J.-G. Rousset, R. Rudniewski, E. Janik, T. Slupinski,P. Kossacki, A. Golnik, and W. Pacuski,
Ultra low density of CdTequantum dots grown by MBE , J. Cryst. Growth , 274 (2013). J. Kobak, T. Smole´nski, M. Goryca, M. Papaj, K. Gietka,A. Bogucki, M. Koperski, J.-G. Rousset, J. Suffczyski, E. Janik,M. Nawrocki, A. Golnik, P. Kossacki, and W. Pacuski,
Designingquantum dots for solotronics , Nat. Commun. , 3191 (2014). T. Smole´nski, W. Pacuski, M. Goryca, M. Nawrocki, A. Golnik,and P. Kossacki,
Optical spin orientation of an individual Mn ion in a CdSe/ZnSe quantum dot , Phys. Rev. B , 045306 (2015). T. Smolenski, T. Kazimierczuk, J. Kobak, M. Goryca, A. Golnik,P. Kossacki, and W. Pacuski,
Magnetic Ground State of an Indi-vidual Fe Ion in Strained Semiconductor Nanostructure , Nat.Commun. , 10484 (2016). J. Suffczy´nski, T. Kazimierczuk, M. Goryca, B. Piechal, A. Tra-jnerowicz, K. Kowalik, P. Kossacki, A. Golnik, K. P. Korona,M. Nawrocki, J. A. Gaj, and G. Karczewski,
Excitation mecha-nisms of individual
CdTe?ZnTe quantum dots studied by photoncorrelation spectroscopy , Phys. Rev. B , 085319 (2006). T. Kazimierczuk, T. Smole´nski, M. Goryca, L. Kłopotowski,P. Wojnar, K. Fronc, A. Golnik, M. Nawrocki, J. A. Gaj, andP. Kossacki,
Magnetophotoluminescence study of intershell ex-change interaction in CdTe/ZnTe quantum dots , Phys. Rev. B ,165319 (2011). T. Kazimierczuk, T. Smole´nski, J. Kobak, M. Goryca, W. Pacuski,A. Golnik, K. Fronc, L. Kłopotowski, P. Wojnar, and P. Kos-sacki,
Optical study of electron-electron exchange interaction inCdTe/ZnTe quantum dots , Phys. Rev. B , 195302 (2013). J. Kobak, W. Pacuski, T. Jakubczyk, T. Kazimierczuk, A. Golnik,K. Frank, A. Rosenauer, C. Kruse, D. Hommel, and J. A. Gaj,
Optical Properties of CdTe QDs Formed Using Zn Induced Reor-ganization , Acta Phys. Pol. A , 627 (2011). M. Zieli´nski, K. Gołasa, M. R. Molas, M. Goryca, T. Kazimier-czuk, T. Smole´nski, A. Golnik, P. Kossacki, A. A. L. Nicolet,M. Potemski, Z. R. Wasilewski, and A. Babi´nski,
Excitonic com- plexes in natural InAs/GaAs quantum dots , Phys. Rev. B ,085303 (2015). A. Kudelski, A. Golnik, J. (Gaj, S. Mackowski, G. Karczewski,and J. Kossut,
Zeeman effect and optical anisotropy in microlu-minescence of self-assembled CdTe/ZnTe quantum dot systems , inProceedings of the 25th International Conference on Physics ofSemiconductors, Springer, Osaka 2000 pp. 1249–1250 (2001). I. Strzalkowski, S. Joshi, and C. R. Crowell,
Dielectric constantand its temperature dependence for GaAs, CdTe, and ZnSe , Appl.Phys. Lett. , 350 (1976). Landolt-Boernstein,
Group III Condensed Matter , Springer-Verlag GmbH (1998). J. Voigt, F. Spiegelberg, and M. Senoner,
Band parameters of CdSand CdSe single crystals determined from optical exciton spectra ,Phys. Status Solidi B , 189 (1979). M. Nawrocki and A. Twardowski,
Oscillatory Magnetoabsorptionin CdTe , Phys. Status Solidi B , K61 (1980). H. Wagner, S. Lankes, K. Wolf, M. Wrz, T. Reisinger, A. Naumov,W. Kuhn, H. Stanzl, and W. Gebhardt,
Resonant photolumines-cence measurements in As- and P-doped ZnTe epilayers , PhysicaB , 169 (1993). G. Aliev, O. Koshchug, and R. Seisyan,
High-temperature effec-tiveness limit of exciton-polariton processes in cadmium and zinctelluride crystals , Phys. Solid State , 203 (1994). M. W¨orz, E. Griebl, T. Reisinger, R. Flierl, B. Haserer, T. Semm-ler, T. Frey, and W. Gebhardt,
Gap Energies, Exciton BindingEnergies and Band Offsets in Ternary ZnMgSe Compounds andZnSe/ZnMgSe Heterostructures , Phys. Status Solidi B202