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(322) Production(s) de GIL B.
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MOVPE GROWTH AND OPTICAL CHARACTERIZATION OF ZNSE/ZNS STRAINED-LAYER SUPERLATTICES
Auteur(s): Aigouy L., Briot N., Bouchara D., Cloitre T., Diblasio M., Gil B., Calas J., Briot O., Aulombard R.
(Article) Publié:
Superlattices And Microstructures, vol. 16 p.71 (1994)
Ref HAL: hal-00547271_v1
Exporter : BibTex | endNote
Résumé: We have grown ZnSe/ZnS superlattices using low pressure MOVPE. The superlattices were grown onto a relaxed ZnSe buffer and were constituted of 45 periods. The well and barrier thicknesses were chosen from the calculation of critical thicknesses for coherent and free standing situations. Following this analysis we have grown samples with individual ZnSe, ZnS thicknesses of 3 to 9 monolayers. The optical properties of the samples were studied using photoluminescence, photoreflectance and reflectivity experiments. The results of the photoluminescence and photoreflectance experiments are consistent with a free standing model of the strain state, and a typical sketch of potential profile, describing the band structure of such superlattices is proposed. The photoluminescence linewidth is analyzed in terms of interface roughness. The asymmetry of the photoluminescence peaks is modelled using a density of state with a low energy exponential tail, due to the competition between radiative recombination and non-radiative recombination mechanisms. In some samples of lower crystalline quality, bound excitons were observed in the near band edge photoluminescence, which we attribute to impurity interdiffusion, which is favoured by crystalline defects.
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REFLECTIVITY ANALYSIS OF ZNS LAYERS GROWN ON GAAS AND SI SUBSTRATES BY METAL-ORGANIC VAPOR-PHASE EPITAXY
Auteur(s): Briot O., Briot N., Abounadi A., Gil B., Cloitre T., Aulombard R.
(Article) Publié:
Semiconductor Science And Technology, vol. 9 p.207 (1994)
Ref HAL: hal-00547286_v1
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Résumé: We have grown high-purity ZnS layers by metal organic vapour-phase epitaxy onto (100) GaAs and (111) Si substrates using triethylamine dimethylzinc. As is usually reported, the morphology and the crystalline quality assessed by the optical Nomarski microscope and by double x-ray diffraction are similar on both substrates. However, we demonstrate for the first time, using reflectivity experiments along with a theoretical fit, that the crystalline quality of the sample deposited onto Si substrates is much poorer. This observation is interpreted in terms of antiphase defects related to the lack of polarity of the Si substrate.
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OPTICAL-PROPERTIES OF WIDE-GAP II-VI ZNTE EPILAYERS
Auteur(s): Averous M., Abounadi A., Aulombard R., Bouchara D., Briot N., Briot O., Calas J., Cloitre T., Gil B.
(Article) Publié:
Physica Status Solidi B, vol. 181 p.427 (1994)
Ref HAL: hal-00547284_v1
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Résumé: The optical properties of ZnTe epilayers grown by low-pressure metal organic vapour phase epitaxy on GaAs and GaSb substrates are studied. The layers are grown by using the halide-free triethylamine dimethylzinc adduct and di-isopropyl telluride as zinc and tellurium precursors, respectively. A detailed analysis of the residual strain is offered as a function of layer thickness and substrate nature via reflectivity measurements performed at pumped liquid helium temperature. This is completed by an extensive analysis of near-band-edge photoluminescence spectra in order to discriminate the contribution of residual impurities. Using these precursors ZnTe layers with extremely low contamination rates are obtained.
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UPPER-CONDUCTION-BAND EFFECTS IN HEAVILY STRAINED LOW-DIMENSIONAL ZINCBLENDE SEMICONDUCTOR SYSTEMS
Auteur(s): Jancu Jm, Bertho D, Jouanin C, Gil B., Pelekanos N, Magnea N, Mariette H
(Autres publications)
, 1994
Résumé: We show the existence of a stress-induced coupling between upper-conduction-band states and valence-band states in bulk zinc-blende semiconductors and in their strained-layer low-dimensional systems. This coupling is calculated by an empirical tight-binding method which exactly includes the full crystal symmetry of the strained semiconductor compounds. As an application, we report a study of CdTe-ZnTe superlattices having thin ZnTe layers which exhibit an anomalously high energy for the electron to light-hole transition. We show that the large shift of this transition is well accounted for via mixing between valence and upper-conduction bands.
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EXCITON BINDING-ENERGIES AND PHOTOINDUCED TUNNELING OF CARRIERS IN (GA,IN)AS-GAAS HETEROSTRUCTURES GROWN WITH BUILT-IN PIEZOELECTRIC FIELD
Auteur(s): Bigenwald P, Boring P, Moore Kj, Gil B., Woodbridge K
(Article) Publié:
Journal De Physique Iv (Proceedings), vol. 4 p.215-223 (1994)
Résumé: We compare the binding energy of interacting electron and hole pairs in double quantum wells with and without internal piezo-electric fields. We show that the exciton binding is less sensitive to the piezo electric field than the oscillator strength. This allows many body-effects and bandgap renormalization to be easily produced in strained-layer quantum wells with internal built-in piezo-electric fields, under photo excitation. Our observation was made at low temperature by comparing the behaviour of Ga0.92In0.08As-GaAs strained layer single and double quantum wells grown along the (001) and (111) directions when the densities of photo-injected carriers are tuned over several decades. Comparison between experimental data and the results of a Hartree calculation including the space charge effects reveals that manybody interactions are efficiently photo-induced in the (Ill)-grown samples. Moreover, tunnelling of the two first excited heavy-hole levels can be stimulated for moderate carrier densities making such structure promissive for realising self electrooptic effect device (SEED) modulators.
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A VARIATIONAL CALCULATION OF LIGHT-HOLE ENVELOPE FUNCTIONS AND EXCITON BINDING-ENERGIES IN (GA, IN)AS-GAAS QUANTUM-WELLS
Auteur(s): Bigenwald P, Gil B.
(Article) Publié:
Solid State Communications, vol. 91 p.33-38 (1994)
Résumé: We have performed a self consistent calculation for both the heavy-hole and light-hole excitons in (Ga, In)As-GaAs quantum wells. The self-consistent light-hole wave function has been found to peak either in the alloy layer or in the GaAs layer, depending both on the indium content and thickness of the (Ga, In)As layer. We have calculated the average light-hole and electron positions and have found that both type I and type II excitons can be obtained from a type II band to band profile with a marginal light-hole potential in agreement with spin orientation measurements.
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REFLECTIVITY AND PHOTOLUMINESCENCE MEASUREMENTS IN ZNS EPILAYERS GROWN BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION
Auteur(s): Abounadi A., Diblasio M., Bouchara D., Calas J., Averous M., Briot O., Briot N., Cloitre T., Aulombard R., Gil B.
(Article) Publié:
Physical Review B, vol. 50 p.11677 (1994)
Ref HAL: hal-00547273_v1
Exporter : BibTex | endNote
Résumé: Thin films of high-quality ZnS were grown on (001) GaAs and (111) Si substrates by metal-organic chemical-vapor deposition. 2-K reflectivity was used to analyze various samples grown at different temperatures. The spectra show two structures at 3.801 eV corresponding to the free exciton and at 3.871 eV corresponding to the E0+Δ0 transition. Theoretical reflectivity spectra were calculated using the spatial dispersion model with two oscillators. Thus, the transverse energies, the longitudinal transversal splitting, the oscillator strengths, and the damping parameters were determined for both the free exciton and the split-off exciton of ZnS. Photoluminescence measurements were also carried out using an excimer laser (308 nm). Both light-hole and heavy-hole excitons were observed, which allow for the determination of the strain that exists in the layer. This strain is due only to the difference between the thermal-expansion coefficients of the GaAs substrate and the ZnS epilayer, and was demonstrated to be a tensile strain. This paper also presents results on the band-gap energy variation as a function of the temperature and photoluminescence spectra when the excitation was varied from weak to very high densities (15 MW/cm2).
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