Caracterisation optique et physique de ZnSe. Etude des macles et des deformations thermoelastiques d'une couche ZnSe sur un substrat. Etude des excitons libres dans des films de ZnSe, des impuretes et defauts dans la couche de ZnSe epitaxique, et de leurs proprietes optiques non lineaires

Optical Properties of ZnSe Epilayers and Films

We present a critical review of the strategies used in the fabrication of mismatched semiconductor heterostructures. By using simple concepts derived from the Matthews model of misfit relief, we show how the relaxation of single layers and complex structures may be analysed and predicted. These techniques allow a broad view of the processes that take place in the relaxation of strained layers. This is followed by a discussion of how the relative misfits and thicknesses of different layers in a heterostructure may influence the behaviour and distribution of dislocations in the structure. Finally, we describe the historical development and status of the experimental work and development that has been carried out in this area.

Plastic relaxation and relaxed buffer layers for semiconductor epitaxy

ZnSe nanoribbons have been synthesized using sputter-coated gold films as catalysts via metalorganic chemical vapor deposition on Si (100) substrates. Both x-ray and selected area electron diffractions determine that they have the zinc-blende structure. High-resolution transmission electron microscopic investigations show that their structure is highly ordered and contains coherent twin lamellae near one edge but is essentially free of dislocations. Photoluminescence studies at 10 K show that sharp excitonic peaks dominate their spectra, reflecting their high purity and nearly perfect stoichiometry. New excitonic peaks are observed in the nanoribbons and their possible origins are discussed.

Structure and photoluminescence of ZnSe nanoribbons grown by metal organic chemical vapor deposition

X‐ray diffraction in thin layers containing small randomly placed defects is described by means of the kinematical diffraction theory and optical coherence formalism. The method enables us to calculate both the diffracted intensity and its angular distribution, so that it can be used for simulating double crystal and triple crystal x‐ray diffractometry experiments. The theory has been applied to experimental data obtained from diffractometry measurements of an epitaxial ZnTe layer with mosaic structure after several steps of chemical thinning. A good agreement of the theory with experiments has been achieved.

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X‐ray double and triple crystal diffractometry of mosaic structure in heteroepitaxial layers

Native defect identification in II–VI materials

Using reflection, photoluminescence and excitation spectroscopy the authors carried out systematic studies on the optical properties in the excitonic energy region of ZnTe/GaAs epilayers grown by hot-wall epitaxy (HWE). They calculate the strain magnitude, the light-hole (lh) and heavy-hole (hh) energy shifts, and compare the theoretical values with the experimentally observed energy positions in ZnTe films of different thicknesses. The detected energy distance between the free excitons Xlh and Xhh decreases with increasing layer thickness, indicating a relaxation of the thermally induced strain in the ZnTe layer. Additionally, the authors investigate the incorporation of different impurities, the electronic structure of the main acceptor-exciton complexes (A0,X) and the high-photon-density spectra of the ZnTe films. For increasing densities a biexciton band appears, and they determine the biexciton binding energy to amount to about 3.3+or-1.0 meV.

https://iopscience.iop.org/article/10.1088/0268-1242/6/9A/016/pdf

Photoluminescence and excitation spectroscopy of ZnTe/GaAs epilayers grown by hot-wall epitaxy

Exciton complexes in ZnSe layers: a tool for probing the strain distribution

Impurity and defect distribution in ZnTe/GaAs epilayers of different thickness

Comparative photoluminescence and excitation spectra of ZnSe/GaAs epilayers grown by molecular beam epitaxy (MBE) and hot‐wall epitaxy (HWE) show likewise features in the exciton energy regime. Two strain‐split components of the free exciton are observed, as well as characteristic sets of transitions from or into ground and excited states of acceptor‐ and donor‐bound excitons. However, all respective lines are shifted to lower energies in the HWE samples, due to the increased thermally induced strain as a consequence of the substrate temperatures being enhanced compared to the MBE growth. Whereas the dominant donors are of the same nature in both kinds of samples, specific acceptor centers are incorporated in the HWE films. Although the MBE‐grown layers are of superior quality, it is shown that HWE under optimized growth conditions is a cheap and useful alternative to obtain ZnSe epilayers of reliable properties.

N. Presser

Papers

Optical Properties of ZnSe Epilayers and Films

Photoluminescence and excitation spectroscopy of ZnTe/GaAs epilayers grown by hot-wall epitaxy

Exciton complexes in ZnSe layers: a tool for probing the strain distribution

Impurity and defect distribution in ZnTe/GaAs epilayers of different thickness

Comparative optical investigations of ZnSe/GaAs epilayers grown by molecular beam and hot‐wall epitaxy