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1

CdSe/ZnCdSe Quantum Dot Heterostructures for Yellow Spectral Range Grown on GaAs Substrates by Molecular Beam Epitaxy

100%

Gronin S., Sorokin S., Kazanov D., Sedova I., Klimko G., Evropeytsev E., Ivanov S.

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vol. 126

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issue 5

1096-1099

EN

This paper reports on theoretical calculations and fabrication by molecular beam epitaxy of wide-gap II-VI heterostructures emitting in the "true" yellow range (560-600 nm) at room temperature. The active region of the structures comprises CdSe quantum dot active layer embedded into a strained Zn_{1-x}Cd_{x}Se (x=0.2-0.5) quantum well surrounded by a Zn(S,Se)/ZnSe superlattice. Calculations of the CdSe/(Zn,Cd)Se/Zn(S,Se) quantum dot-quantum well luminescence wavelength performed using the envelope-function approximation predict rather narrow range of the total Zn_{1-x}Cd_{x}Se quantum well thicknesses (d ≈ 2-4 nm) reducing efficiently the emission wavelength, while the variation of x (0.2-0.5) has much stronger effect. The calculations are in a reasonable agreement with the experimental data obtained on a series of test heterostructures. The maximum experimentally achieved emission wavelength at 300 K is as high as 600 nm, while the intense room temperature photoluminescence has been observed up to λ =590 nm only. To keep the structure pseudomorphic to GaAs as a whole the tensile-strained surrounding ZnS_{0.17}Se_{0.83}/ZnSe superlattice were introduced to compensate the compressive stress induced by the Zn_{1-x}Cd_{x}Se quantum well. The graded-index waveguide laser heterostructure with a CdSe/Zn_{0.65}Cd_{0.35}Se/Zn(S,Se) quantum dot-quantum well active region emitting at λ =576 nm (T=300 K) with the 77 to 300 K intensity ratio of 2.5 has been demonstrated.

2

Optical and Structural Properties of GaAs/AlGaAs Quantum Wells Grown by MBE in the Vicinity of As-Rich-GaAs/ZnSe Heterovalent Interface

100%

Klimko G., Evropeytsev E., Sitnikova A., Gronin S., Sedova I., Sorokin S., Ivanov S.

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vol. 126

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issue 5

1184-1186

EN

The studies of structural and optical properties of molecular beam epitaxy grown pseudomorphic hybrid structures with AlGaAs/GaAs quantum well placed closely to the GaAs/ZnSe heterointerface are presented. The interfaces were formed in different ways (Zn or Se initial GaAs surface exposure, different growth temperature and ZnSe growth mode) on As-rich c(4×4) and (2×4) GaAs surfaces. It has been demonstrated that the photoluminescence intensity from the near-heterointerface GaAs QW is influenced most significantly by the procedure of ZnSe growth initiation. The bright photoluminescence (77 K) from the near-interface GaAs quantum well is observed if the Se-decoration procedure is used during the GaAs/ZnSe heterointerface formation on (2×4)As GaAs surface. It reduces noticeably if the GaAs reconstruction changes to c(4×4)As and disappears completely when Zn pre-exposure of GaAs surface is used. These effects are discussed in terms of different ratio of Ga-Se and As-Zn bonds at the GaAs/ZnSe heterointerface resulting in different band offsets and/or uncompensated built-in electric fields.

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Structural and Optical Properties of Alternately-Strained ZnS_{x}Se_{1-x}/CdSe Superlattices with Effective Band-Gap 2.5-2.6 eV

84%

Evropeytsev E., Sorokin S., Gronin S., Sedova I., Klimko G., Sitnikova A., Baidakova M., Ivanov S., Toropov A.

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vol. 126

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issue 5

1156-1158

EN

We report on design and fabrication of alternately-strained ZnS_xSe_{1-x}/CdSe short period superlattices with the effective band-gap 2.52, 2.58, and 2.61 eV and the total thickness ≈300 nm. Transmission electron microscopy, X-ray diffraction, and photoluminescence measurements reveal negligibly small density of misfit dislocations in the superlattices. The investigation of carrier transport along the superlattice growth axis, performed by the photoluminescence measurements of a superlattice with one enlarged quantum well, confirms efficient Bloch-type transport at temperatures above ≈ 100 K. Such superlattices look promising for the applications as a material for the wide band-gap photoactive region of a multi-junction solar cell comprising both III-V and II-VI materials.

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3 Acta Physica Polonica A

3 2014

3 Evropeytsev E.

3 Gronin S.

3 Ivanov S.

3 Klimko G.

3 Sedova I.

3 Sorokin S.

2 Sitnikova A.

1 Baidakova M.

1 Kazanov D.

1 Toropov A.

CdSe/ZnCdSe Quantum Dot Heterostructures for Yellow Spectral Range Grown on GaAs Substrates by Molecular Beam Epitaxy

Optical and Structural Properties of GaAs/AlGaAs Quantum Wells Grown by MBE in the Vicinity of As-Rich-GaAs/ZnSe Heterovalent Interface

Structural and Optical Properties of Alternately-Strained ZnS_{x}Se_{1-x}/CdSe Superlattices with Effective Band-Gap 2.5-2.6 eV