Home  About us  Contact
 

Multi Quantum (multi + quantum)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Three-dimensionally structured silicon as a substrate for the MOVPE growth of GaN nanoLEDs

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2009
Sönke Fündling
Abstract Three-dimensionally patterned Si(111) substrates are used to grow GaN based heterostructures by metalorganic vapour phase epitaxy, with the goal of fabricating well controlled, defect reduced GaN-based nanoLEDs. In contrast to other approaches to achieve GaN nanorods, we employed silicon substrates with deep etched nanopillars to control the GaN nanorods growth by varying the size and distance of the Si pillars. The small footprint of GaN nanorods grown on Si pillars minimise the influence of the lattice mismatched substrate and improve the material quality. For the Si pillars an inductively coupled plasma dry-etching process at cryogenic temperature has been developed. An InGaN/GaN multi quantum well (MQW) structure has been incorporated into the GaN nanorods. We found GaN nanostructures grown on top of the silicon pillars with a pyramidal shape. This shape results from a competitive growth on different facets as well as from surface diffusion of the growth species. Spatially resolved optical properties of the structures are analysed by cathodoluminescence. Strongly spatial-dependent MQW emission spectra indicate the growth rate differences on top of the rods. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Annealing experiments of the GaP based dilute nitride Ga(NAsP)

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2008
B. Kunert
Abstract The post-growth annealing behaviour of Ga(NAsP) multi quantum well heterostructures (MQWHs) grown pseudomorphically strained to GaP substrate has been investigated. The optical properties as well as the structural crystal quality of the novel dilute nitride show an obvious dependence on the applied annealing temperature. Photoluminescence (PL) measurements reveal a step-like blue shift of the PL peak position in line with an increase of PL intensity with rising annealing temperature. The PL line width decreases to a mini- mal value for an optimized heating temperature around 800 °C. This annealing behaviour of the Ga(NAsP)/GaP-MQWHs up to 850 °C is quite typical for a dilute nitride, however, the functional dependence of the integrated intensity above 850 °C is unusual. The increase of the PL line width above 850 °C suggests a deterioration of the crystalline MQW quality, but transmission electron microscopy (TEM) and high resolution X-ray diffraction (XRD) prove the opposite. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Optical properties of InGaN/GaN MQW microdisk arrays on GaN/Si(111) template

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
Kang Jea Lee
Abstract We report the fabrication of InGaN/GaN multi quantum well (MQW) microdisk arrays on Si(111) substrates. InGaN/GaN MQWs were grown on highly tensile-strained GaN films on Si(111) substrate by metalorganic chemical vapor deposition. Microdisk resonators were fabricated using a combination of optical lithography, a dry GaN-etching process, and Si undercut etching by acid chemical solution. The evidence of whispering-gallery modes in optically pumped microdisk cavities have been observed by photoluminescence. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Cathodoluminescence, High-Resolution X-Ray Diffraction and Transmission-Electron-Microscopy Investigations of Cubic AlGaN/GaN Quantum Wells

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003
D.J. As
Abstract The structural and optical properties of cubic Al0.25Ga0.75N/GaN multi quantum well structures grown on GaAs (001) substrates by radio-frequency plasma-assisted molecular beam epitaxy (MBE) are reported. Transmission electron microscopy (TEM), high resolution X-ray diffraction (HRXRD), and cathodoluminescence (CL) measurements are used to characterize the cubic Al0.25Ga0.75N/GaN quantum wells. The interfaces between the quantum-well and barrier layers are well resolved, abrupt and the entire structure shows an excellent periodicity. Due to the high dislocation density of about 1010 cm,2 a severe broadening of the XRD-reflection is observed and superlattice satellite peaks are only weakly indicated. Further, a wavy structure is seen in TEM at the coalescence of submicron-size grains. Nevertheless, CL at room temperature shows a strong emission of quantized states at 3.352 eV. [source]