Applications of multiple-crystal diffractometry

Fewster, Paul F.; Andrew, N. L.

doi:10.1088/0022-3727/28/4a/019

Cited by 61 publications

(30 citation statements)

References 10 publications

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“…For temperature dependent ͑10-300 K͒ spectroscopic measurements, QW sample is mounted in a closed cycle helium refrigerator. HRXRD measurements are performed by using an PANalytical X'PERT diffractometer, 20 equipped with a Ge ͑220͒ monochromator ͑Bartels type, four reflections͒, with a beam divergence of ϳ12 arc sec in the scattering plane for Cu K␣ 1 x-rays ͑ = 1.5406 Å͒. All HRXRD measurements are done with a 1°open detector in a plane parallel to the scattering plane.…”

Section: Methodsmentioning

confidence: 99%

Temperature dependence of the lowest excitonic transition for an InAs ultrathin quantum well

Singh

Porwal

Sharma

et al. 2006

Journal of Applied Physics

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Temperature dependent photoluminescence and photoreflectance techniques are used to investigate the lowest excitonic transition of InAs ultrathin quantum well. It is shown that the temperature dependence of the lowest energy transition follows the band gap variation of GaAs barrier, which is well reproduced by calculated results based on the envelope function approximation with significant corrections due to strain and temperature dependences of the confinement potential. A redshift in photoluminescence peak energy compared to photoreflectance is observed at low temperatures. This is interpreted to show that the photoluminescence signal originates from the recombination of carriers occupying the band-tail states below the lowest critical point.

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Section: Methodsmentioning

confidence: 99%

Temperature dependence of the lowest excitonic transition for an InAs ultrathin quantum well

Singh

Porwal

Sharma

et al. 2006

Journal of Applied Physics

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“…2, we present one of the RLP map of asymmetric (10 15) reflection. Following Fewster's analysis, the direction of the main axis of the RLP relates to tilted growth, while the elliptical spreading parallel to Q x -axis correlates with lateral mosaic block size [12,13]. It is seen that the shape of RLP in Fig.…”

Section: Resultsmentioning

confidence: 86%

“…While it is important that rocking curves for evaluating twist be taken under quasi-symmetric geometry, rather than asymmetric geometry, the 2-D intensity distribution of the reciprocal lattice point (RLP) from an asymmetric reflection is affected mostly by the combination of the following: lattice variation in the direction of surface normal, tilt, and lateral correlation length [12,13]. In Fig.…”

Section: Resultsmentioning

confidence: 99%

X‐ray characterization of high quality AlN epitaxial layers: effect of growth condition on layer structural properties

Paduano

Drehman

Weyburne

et al. 2003

phys. stat. sol. (c)

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.72. Dd, 68.55.Jk AlN layers were deposited directly on (0001) sapphire by a MOCVD two-step pressure process. The best (0002) and (10 12) rocking curves had FWHM values of ~360 arcsec and ~580 arcsec respectively. A detailed X-ray diffraction study was carried out to investigate the effect of growth condition on the layer structural properties. In-plane twist was estimated from the FWHM values of both ω-scans and φ-scans as functions of inclination angle, using the quasi-symmetrical reflection from a group of lattice planes with inclination angle ranging from 0 to 75°. The range of twist spread was found to be sensitive to the substrate nitridation condition. The lowest spread angle obtained with optimized nitridation was ~770 arcsec. As expected, the edge-type threading dislocation density estimated from twist spreading was found to correlate well with the dislocation density measured by TEM. The tilt spreading was found to be sensitive to the growth pressure. By reducing growth pressure to 40 Torr, we obtained layers with tilt spreading less than 120 arcsec. 1 Introduction There is increasing interest in the growth of high quality AlN because of its high temperature stability, high electrical resistivity, high thermal conductivity, UV transparency, and good lattice match with GaN. These properties make AlN a promising substrate for various high power, high temperature electronic and opto-electronic applications. Indeed, recent reports have shown that InGaN based LEDs [1] and GaN HEMTs [2] grown on AlN/sapphire template have substantially improved device performance. Since AlN substrates are not available, heteroepitaxial AlN films are usually deposited on foreign substrates. These AlN films often contain high densities of structural defects. Recently, we reported the development of a two-step pressure process for AlN growth on sapphire substrates [3]. With an optimum nitridation condition, we showed that the new process was effective for the improvement of crystalline quality of AlN films.To understand the effect of growth conditions on the layer structural properties, we undertook a detailed X-ray diffraction study. AlN films usually exhibit a high degree of mosaicity; i.e. the films consist of sub-grains slightly misoriented with respect to each other and the underlying substrate. Such structure is usually described by a spread of tilt angles with respect to substrate normal and a range of twist angles in the basal plane. This spreading contributes to the broadening of the width of the X-ray diffraction peaks. The methods reported in the literature to characterize such twist, however, vary from group to group: some use rocking curves of a quasi-symmetric or a symmetric reflection [4,5], while others

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Section: 1´óèøñôçäââ óçðõåçðñäôíââ Aeë×óâíõñïçõóëâunclassified

High-resolution X-ray diffraction in crystalline structures with quantum dots

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2015

Usp. Fiz. Nauk

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Applications of multiple-crystal diffractometry

Cited by 61 publications

References 10 publications

Temperature dependence of the lowest excitonic transition for an InAs ultrathin quantum well

Temperature dependence of the lowest excitonic transition for an InAs ultrathin quantum well

X‐ray characterization of high quality AlN epitaxial layers: effect of growth condition on layer structural properties

High-resolution X-ray diffraction in crystalline structures with quantum dots

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