Wide-band-gap ZnMgBeSe alloys grown onto GaAs by molecular beam epitaxy (original) (raw)
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Molecular beam epitaxy and optical properties of ZnCdS/ZnMgS quantum wells on GaP
Journal of Crystal Growth, 2000
We report the growth of ZnCdS/ZnMgS quantum wells (QWs) and their optical properties. The constituent alloy layers were grown by molecular beam epitaxy under a large S #ux and a high substrate temperature. The layers exhibit high quality in terms of double crystal X-ray rocking curve and optical spectra including photoluminescence (PL), PL excitation and re#ection spectra. The ZnCdS/ZnMgS QWs exhibit strong emission from the ZnCdS well(s) through photo-excitation at the ZnMgS barriers. By changing the growth condition of the QW structures, PL line width can be reduced. Such QWs show PL up to room temperature.
Low pressure MOVPE growth and structural properties of ZnMgSe epilayers on (100)GaAs
Journal of Crystal Growth, 2000
The low-pressure MOVPE growth of ZnMgSe on (1 0 0)GaAs is reported. ZnMgSe alloys were deposited after a thin pseudomorphic ZnSe bu!er layer by using dimethylzinc : triethylammine (Me Zn : Et N), ditertiarylbutilselenide (Bu Se) and bis(methylcyclopentadienyl)magnesium [(MeCp) Mg]. Zn \V Mg V Se (0.10(x(0.46) epilayers were grown at 3303C, 304 mbar and a high VI/II ratio in the vapour. Under these conditions the growth is limited by the mass transport of the II-group alkyls and good control of the composition was achieved. Rutherford backscattering spectrometry measurements allowed to determine the epilayer stoichiometry and deposited dose. The ZnMgSe solid}vapour distribution curve deviates from linearity due to the di!erent Mg and Zn alkyl vapour di!usion coe$cients, whose ratio turns out to be D + ! + /D + 8 "0.410. The epilayer crystalline properties were studied by double-crystal X-ray di!raction (DC-XRD) and high-resolution reciprocal space mapping (RSM) measurements. Rocking curve FWHM values of 540}900 nm thick Zn \V Mg V Se were in the 5}12 mrad range, indicating the occurrence of extended defects in the epilayers. RSM measurements in the vicinity of the (400)-peak of a Zn Mg Se/ZnSe/(1 0 0)GaAs sample showed a slight asymmetry of the ternary alloy peak along the growth direction, ascribed to an inhomogeneous relaxation of the epilayer. (P. Prete). blue}green light emitting laser diodes (LDs), in the form of GaAs-matched ZnMgSSe cladding layers for photon con"nement or quantum well barriers for the LD active region . Interest in the ZnMgSe ternary alloy has raised, for it borders the ZnMgSSe compound and its study helps to determine the structural and electronic properties of the quaternary alloys. Also, ZnMgSe/ZnSe quantum wells have been studied for the realisation 0022-0248/00/$ -see front matter
Energy band gaps of Zn1−xMgxSySe1−y lattice matched to GaAs
Physica B: Condensed Matter, 2003
We report on theoretical study of the energy band gaps for the quaternary alloys Zn 1Àx Mg x S y Se 1Ày in conditions of lattice matching to GaAs substrates using simply the empirical pseudopotential method under the virtual crystal approximation which takes into account the effects of compositional disorder. Our results agree generally very well with the available experimental data. It is shown that the band-gap energies of Zn 1Àx Mg x S y Se 1Ày are expressed by the parabolic function of the composition considering the bowing parameter and that Zn 1Àx Mg x S y Se 1Ày can be a direct or an indirect semiconductor depending on the alloy composition. The Zn 0:35 Mg 0:65 S 0:6 Se 0:4 is predicted to meet requirement of the cladding layer for fabricating blue double heterostructure laser diodes using ZnS 0:06 Se 0:94 as the active layer.
Journal of Applied Physics, 1998
ZnSe films with thickness between 800 and 7500 Å were grown on GaAs͑100͒ by molecular beam epitaxy ͑MBE͒, and characterized by photoluminescence ͑PL͒, photoreflectance ͑PR͒, transmission electron microscopy ͑TEM͒, and high resolution x-ray diffraction. A first set of films was prepared with ZnSe directly grown on the GaAs substrate. Another set was prepared using an arsenic capped GaAs buffer layer grown on the GaAs substrate in a separated MBE system. PL studies at 18 K showed that the ZnSe films have more defects for samples grown directly on the GaAs substrate. The behavior of stacking faults and dislocations as a function of film thickness were investigated by TEM, and by the variation of the intensity of PL signals related to these defects. For both sets of samples the intensity of these signals decreased with increasing film thickness, but the decrease is steeper for films grown on GaAs buffer layers. A signal in PL spectra at ϳ2.7 eV was observed only for the samples grown directly on GaAs substrates, it was associated with donor-acceptor transitions involving Ga Zn and V Zn . The room temperature PR spectra showed, besides the GaAs and ZnSe band-gap signals, oscillations associated with the Franz-Keldysh effect due to internal electric fields. The strength of these fields was obtained by employing the asymptotic Franz-Keldysh model. A signal 22 meV below the GaAs band-gap energy was observed only in the PR spectra of the samples grown directly on GaAs substrates. This signal was associated with Zn interdiffused into the GaAs, and is correlated to the PL signal observed at 2.7 eV for the same set of samples.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1999
ZnSe-based II-VI ternary alloys, such as ZnBeSe, ZnMgSe, and ZnCdSe, have been shown to be excellent candidates for light-emitting device applications in the short-wavelength visible range. Since design of optical semiconductor devices requires knowledge of refractive indices of all materials involved, we studied refractive indices of Zn 1Ϫx Be x Se, Zn 1Ϫx Mg x Se, and Zn 1Ϫx Cd x Se epitaxial layers. The samples were grown by molecular-beam epitaxy in mole fractions ranges between 0рxр0.81, 0рxр0.59, and 0рxр0.57 for Zn 1Ϫx Be x Se, Zn 1Ϫx Mg x Se, and Zn 1Ϫx Cd x Se, respectively. The alloy concentration x was determined by x-ray diffraction. All samples exhibited very high crystalline quality, even at relatively high values of x. A prism-to-film coupler technique, which involves optical tunneling via evanescent fields, was employed to accurately determine the indices of refraction. The variation of the refractive index with alloy composition at room temperature was determined at the wavelength of 632.8 nm.
Journal of Electronic Materials, 2016
Heterostructure p-(ZnMgTe/ZnTe:N)/CdTe/n-(CdTe:I)/GaAs was evaporated using molecular beam epitaxy and investigated for photovoltaic energy conversion application. The electrical properties of the studied heterostructure were measured and characterized in order to understand the relevant electrical transport mechanisms. Electrical properties derived from the currentvoltage (I-V) characteristics of solar cells provide essential information necessary for the analysis of performance losses and device efficiency. I-V characteristics are investigated in dark conditions and under different light intensities. All the electrical and power parameters of the heterostructure were measured, calculated and explained.
Molecular beam epitaxial growth and characterization of zinc-blende ZnMgSe on InP (001)
Applied Physics Letters, 2004
High crystalline quality zinc-blende structure Zn ͑1−x͒ Mg x Se epitaxial layers were grown on InP (001) substrates by molecular beam epitaxy. Their band gap energies were determined as a function of Mg concentration and a linear dependence was observed. The band gap of the Zn ͑1−x͒ Mg x Se closely lattice matched to InP was found to be 3.59 eV at 77 K and the extrapolated value for zinc-blende MgSe was determined to be 3.74 eV. Quantum wells of Zn ͑1−x͒ Cd x Se with Zn ͑1−x͒ Mg x Se as the barrier layer were grown which exhibit near ultraviolet emission.
Growth and properties of wide bandgap (MgSe)n(ZnxCd1−xSe)m short-period superlattices
Journal of Crystal Growth, 2017
We report the molecular beam epitaxy (MBE) growth and properties of (MgSe) n (Zn x Cd 1-x Se) m short-period superlattices(SPSLs) for potential application in II-VI devices grown on InP substrates. SPSL structures up to 1 μm thick with effective bandgaps ranging from 2.6 eV to above 3.42 eV are grown and characterized, extending the typical range possible for the Zn x Cd y Mg 1-x-y Se random alloy beyond 3.2 eV. Additionally, Zn x Cd 1-x Se single and multiple quantum well structures using the SPSL barriers are also grown and investigated. The structures are characterized utilizing reflection high-energy electron diffraction, X-ray reflectance, X-ray diffraction and photoluminescence. We observed layer-by-layer growth and smoother interfaces in the QWs grown with SPSL when compared to the Zn x Cd y Mg 1-x-y Se random alloy. The results indicate that this materials platform is a good candidate to replace the random alloy in wide bandgap device applications.