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  • 1
    Electronic Resource
    Electronic Resource
    Zero-dimensional excitons in CdTe/ZnTe nanostructures (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4936-4943 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin CdTe layers embedded in ZnTe matrix grown by atomic layer epitaxy have been studied by time resolved spectroscopy and spatially resolved spectroscopy. The presence of Cd-rich dotlike islands in these CdTe nanostructures is shown by both atomic force microscopy and high resolution transmission electron microscopy. Zero-dimensional nature of excitons is shown both by the temperature dependence of the decay time and observation of sharp exciton lines in microphotoluminescence spectra. Zero-dimensional excitons probed by microphotoluminescence present a doublet structure linearly polarized along two orthogonal directions. This doublet structure is attributed to bright heavy-hole exciton states split by the local asymmetry of the localization potential. Reversible spectral shifts in the emission of some single quantum dots are observed on a time scale of hundreds of milliseconds. These small shifts can be attributed to the Stark effect caused by fluctuating electric fields and can significantly affect time-integrated transition linewidths. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1436560
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  • 2
    Electronic Resource
    Electronic Resource
    Atomic-layer epitaxy of GaN quantum wells and quantum dots on (0001) AlN (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5498-5500 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that a dynamically stable Ga film is formed on (0001) AlN in a large range of Ga fluxes at a substrate temperature of 740 °C. This feature allows for atomic layer epitaxy (ALE) of GaN on AlN by alternate exposure to Ga and N flux. We show that, at a growth temperature of 740 °C, one ALE cycle leads to the formation of a two-dimensional GaN layer, whereas further cycles lead to the formation of GaN quantum dots following a Stranski–Krastanov growth mode. This behavior is confirmed by atomic force microscopy, transmission electron microscopy, and cathodoluminescence. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1458049
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  • 3
    Electronic Resource
    Electronic Resource
    Atomic layer epitaxy and molecular beam epitaxy of CdTe/MnTe superlattices: A structural and optical study (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4300-4308 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomic layer epitaxy (ALE) is investigated together with conventional molecular beam epitaxy (MBE) for the growth of CdTe/MnTe superlattices. A systematic structural and magneto-optical study demonstrates that: (i) all Mn atoms incident on the surface get incorporated; however, when a quantity superior or equal to 1 monolayer of Mn is sent onto the surface per ALE cycle, the growth front roughens, leading to the formation of MnTe islands, (ii) optimized atomic layer epitaxy allows us to obtain at 280 °C CdTe/MnTe superlattices with a better control than in conventional MBE, but does not prevent the exchange between Cd and Mn atoms from occurring at the interfaces, (iii) low temperature ALE (200 °C and lower) seems to be a promising way of obtaining more abrupt interfaces. A precise value of the ratio of the elastic coefficients 2c12/c11 is otherwise inferred through this study for zincblende MnTe (1.12). © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368648
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  • 4
    Electronic Resource
    Electronic Resource
    Ohmic contacts on n-type CdTe and CdZnTe using coherently grown neodymium (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 514-516 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low resistance metallic contacts have been realized on n-type doped CdTe and CdZnTe layers grown by molecular beam epitaxy. The n-type doping of the layers was achieved using iodine or indium as a dopant. The metal/II–VI semiconductor heterostructures were realized with neodymium that was found to grow coherently on CdTe and CdZnTe substrates, with formation of a reacted compound at the interface. This interfacial layer is noted IL(Nd). The specific contact resistance, ρc, of the Nd/IL(Nd)/n-CdTe and Nd/IL(Nd)/n-CdZnTe heterostructures was measured using the transmission line model. The best result of 2.5×10−5 Ω cm2 is obtained for Nd/IL(Nd)/n-CdTe and for a doping level of about 6×1018 cm−3. An exponential increase of the ρc value is found when increasing zinc concentration in the CdZnTe alloys. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117771
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  • 5
    Electronic Resource
    Electronic Resource
    Quantitative interfacial profiles in CdTe/Mn(Mg)Te heterostructures (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 756-764 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured by high resolution transmission electron microscopy (HRTEM) the width of interfaces in two II–VI heterostructures: CdTe/MnTe and CdTe/MgTe, as a function of the growth mode. A critical review of the different parameters involved in the direct determination of the chemical profile by HRTEM enables us to precisely determine the sensitivity and accuracy of the methods on these particular materials. The measured interface width is of the order of 2.5–3 monolayers (ML) and is compatible with an exchange mechanism involving the monolayer being grown and the last deposited monolayer. Several growth procedures were compared: conventional molecular beam epitaxy and atomic layer epitaxy (ALE). In the case of saturated and oversaturated ALE the inverse MnTe/CdTe interface is no longer planar. A destabilization of the growth front occurs when one or more Mn monolayers per cycle are deposited, through the formation of MnTe islands. Thermal interdiffusion seems to be negligible in the case of Mn. The present HRTEM values for the interface widths extend the results obtained by magneto-optical measurements to higher concentration values and confirm the exchange mechanism. The higher value obtained by x-ray reflectivity (4.7 ML) is explained by the large difference of the average volume on which the measurement is performed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368134
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  • 6
    Electronic Resource
    Electronic Resource
    Growth kinetics and optical properties of self-organized GaN quantum dots (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7618-7624 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Self-organized GaN islands of nanometric scale were fabricated by controlling the Stranski–Krastanov growth mode of GaN deposited by molecular beam epitaxy on AlN. Evidence for ripening of dots under vacuum has been observed, resulting in changes in dot size distribution. We also show that in superlattice samples, consisting of multiple layers of GaN islands separated by AlN, the GaN islands are vertically correlated provided that the AlN layer thickness remains small enough. The luminescence peak of GaN dots is blueshifted with respect to bulk emission and its intensity does not vary with temperature, both effects demonstrating the strongly zero-dimensional character of these nanostructures.© 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367878
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  • 7
    Electronic Resource
    Electronic Resource
    Growth of aluminum nitride on (111) silicon: Microstructure and interface structure (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2003-2009 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of hexagonal aluminum nitride directly on (111) silicon has been studied by grazing incidence x-ray diffraction and high resolution electron microscopy as a function of film thickness. Two epitaxial relationships were observed: (1) AlN (0001) [2110]//Si(111) [022¯], which prevails at deposition temperatures larger than 650 °C, and (2) AlN (0001) [101¯0]//Si(111) [022¯]. For a 40 Å thick layer, the average in-plane crystallite size is 162 Å, the in-plane rotation is ∼2° and the dislocations induce an average strain distribution of 0.8%. The Si/AlN interface is very sharp and complete relaxation (down to ∼0.2%) occurs within one bilayer. No long range order was observed at the interface. This implies a low mobility of the AlN species on Si, inhibiting any structural rearrangement. In particular the in-plane rotations originate from the early stage of the layer growth and decrease with the layer thickness, especially for thicknesses larger than 250 Å. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366929
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  • 8
    Electronic Resource
    Electronic Resource
    Quantitative characterization of GaN quantum-dot structures in AlN by high-resolution transmission electron microscopy (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3287-3289 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN/AlN heterostructures grown by molecular beam epitaxy are studied by high-resolution transmission electron microscopy (HRTEM). The two-dimensional/three-dimensional Stranski–Krastanow growth mode transition of GaN allows the formation of GaN quantum-dot structures embedded in AlN. The nature of the wetting layer associated with these dots is determined by quantitative HRTEM analysis, based on comparison between interplanar distortion profiles of experimental and simulated images. This study demonstrates a low intermixing between GaN and AlN materials. Such result is also evidenced for the GaN dots. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123321
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  • 9
    Electronic Resource
    Electronic Resource
    Polarity determination of GaN films by ion channeling and convergent beam electron diffraction (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2480-2482 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By using ion channeling and convergent beam electron diffraction techniques, we have determined the absolute polarity of various GaN films grown by MOCVD on (0001) sapphire. We observe two main classes of GaN films, namely flat and rough pyramidal ones. We find that flat GaN films have a Ga polarity. Rough pyramidal samples contain many tiny columnar inversion domains (with Ga polarity) imbedded in a matrix exhibiting an N polarity. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117504
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  • 10
    Electronic Resource
    Electronic Resource
    Preferential nucleation of GaN quantum dots at the edge of AlN threading dislocations (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2632-2634 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on transmission electron microscopy and optical characterization of GaN dots embedded in an AlN matrix. GaN dots were grown by molecular beam epitaxy on top of an AlN layer deposited on (0001) sapphire. We found that the GaN dots (average diameter of 16 nm, average height of 4 nm) are coherently grown on AlN, but nucleate next to threading edge dislocations that were propagating in AlN. The presence of these adjacent dislocations does not inhibit the optical emission of the GaN dots: contrary to the photoluminescence of thick GaN layers or GaN/AlGaN quantum wells, the photoluminescence of these GaN dots is found to be temperature independent. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125101
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