Home  About us  Contact
 

Nucleation Layer (nucleation + layer)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

MOVPE growth and characterization of a -plane AlGaN over the entire composition range

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010
Masihhur R. Laskar
Abstract We report the metal organic vapor phase epitaxy (MOVPE) growth and characterization of non-polar (110) a -plane Alx Ga1,xN on (102) r -plane sapphire substrates over the entire composition range. Alx Ga1,xN samples with ,0.8 ,m thick layers and with x = 0, 0.18, 0.38, 0.46, 0.66, and 1.0 have been grown on r -plane sapphire substrates. The layer quality can be improved by using a 3-stage AlN nucleation layer and appropriate V/III ratio switching following nucleation. All a -plane AlGaN epilayers show an anisotropic in-plane mosaicity, strongly influenced by Al incorporation and growth conditions. Careful lattice parameter measurements show anisotropic in-plane strain that results in an orthorhombic distortion of the hexagonal unit cell, making Al composition determination from X-ray diffraction difficult. In general lower Al incorporation is seen in a -plane epilayers compared to c -plane samples grown under the same conditions. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Self-organized nucleation layer for the formation of ordered arrays of double-walled TiO2 nanotubes with temperature controlled inner diameter

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5-6 2010
Mihai Enachi
Abstract It is proposed to use the variation of the electrolyte temperature to fabricate titania nanotubes with variable inner diameter at a constant outer diameter and an invariable package density. The anodization of Ti sheets in an ethylene glycol and HF containing electrolyte is found to allow the preparation of nanotubes with the inner diameter controlled in the range from 10 nm to more than 250 nm through the change of the electrolyte temperature from ,20 °C to +50 °C. The peculiarities of the anodization process performed at low electrolyte temperatures are discussed. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Epitaxial lateral overgrowth of GaN on 4 inch Si(111) by MOVPE

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
Kai Cheng
Abstract Epitaxial Lateral Overgrowth (ELOG) of GaN on 4 inch silicon(111) substrates by MOVPE was investigated in this study. ELOG was performed on a GaN template with a couple of AlGaN intermediate layers (IL) on an AlN nucleation layer. The AlGaN ILs supply compressive stress to the top GaN template and thereafter to the ELOG layer. Consequently, layer cracking is minimized. Two masks were used in this work: a 2 inch wagon wheel mask and a 4 inch mask with parallel stripes of various filling factors and periods. The filling factor is varied from 0.33 to 0.7. The periodic spacing is in the range of 6 ,m to 10 ,m. Temperature, V/III ratio, pressure and stripe orientation were optimized to achieve fastest lateral growth rate. The highest lateral to vertical ratio can be more than 4. A fully coalesced layer within the critical thickness for a crack-free layer was achieved on 4 inch silicon substrates. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Direct MOVPE- and MBE-growth of a-plane GaN on r-plane sapphire

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
T. Aschenbrenner
Abstract We report on the growth of pit-free a-plane GaN on (102) sapphire (r-plane) substrates by metal organic vapor phase epitaxy (MOVPE) using a three step growth method without low temperature nucleation layer. X-ray diffraction , -scans of the symmetric GaN (11-20) reflex revealed for 1.2 ,m thick crack- and pit-free GaN layers low FWHM of 885 arcsec and 2484 arcsec measured by inclination in c- and m-direction, respectively. To analyze the evolution growth was stopped at different stages and the samples were measured with AFM, SEM, and XRD. Furthermore, we discuss the overgrowth of MOVPE GaN layer with molecular beam epitaxy (MBE). For smooth MOVPE templates with closed surfaces the morphology was reproduced, whereas for not coalesced thinner layers a different growth mode and a smoothening of the layers occurred. We will discuss SEM- and AFMdata in detail to examine this overgrowth procedure. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Two-step growth of InGaN quantum dots and application to light emitters

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007
T. Yamaguchi
Abstract A two-step growth method for creating InGaN quantum dots (QDs) was developed by using a combination of an InxGa1,xN nucleation layer (NL) without island structures and an InyGa1,yN formation layer (FL) with an indium content lower than that of the InxGa1,xN NL. The realization of QDs was confirmed by micro-photoluminescence (,-PL) measurements only for the sample with both the InxGa1,xN NL and the InyGa1,yN FL. The spectral position of the QD ensemble recombination was controlled mainly by the deposition time of the InxGa1,xN NL. Green (,520 nm) and amber (,600 nm) LEDs with the QD layers grown by the two-step growth method as the active region were also fabricated and compared with that having InGaN QW layers, reported previously. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Observations on surface morphologies and dislocations of a-plane GaN grown by metal organic chemical vapor deposition

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007
T. S. Ko
Abstract In this study, we grew non-polar a-plane GaN thin films on r-plane sapphire using a series of growth conditions by metal-organic chemical vapor deposition. The results showed that high temperature and low-pressure conditions benefited two-dimension growth could lead to a fully coalesced a-plane GaN layer with a very smooth surface. The best surface morphology with an excellent mean roughness of 10.5 Å was obtained. The different thickness AlN as a nucleation layer and the different ,/, ratio were also considered. The results revealed that the surface morphology would get worse when the thickness of nucleation layer and ,/, ratio were away from the values of optimal condition. The observation of transmission electronic microscopy shown the lowest density of threading dislocations was 1.85×1010/cm2. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Investigations of InSb-based quantum dots grown by molecular-beam epitaxy

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2007
N. Deguffroy
Abstract InSb quantum dots (QDs) have been grown by molecular-beam epitaxy (MBE) on GaSb substrates. Typical MBE growth conditions lead to a low density (,109 cm,2) of large islands which are dislocated. Insertion of a thin InAs nucleation layer increases the QDs density by one order of magnitude which is interpreted in terms of differing In-to-group-V binding energies. Finally, we show that a high density (,7 x 1010 cm,2) of small coherent QDs can be grown by using a two-steps procedure. Photoluminescence near 3.5 µm is demonstrated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A novel approach for the growth of InGaN quantum dots

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2006
T. Yamaguchi
Abstract A novel two-step growth method for creating InGaN quantum dots (QDs) was developed by using a combination of an InxGa1,xN nucleation layer with a platelet structure and an InyGa1,yN formation layer with an indium content lower than that of the InxGa1,xN nucleation layer. The realized QDs were investigated by micro-photoluminescence measurements. We observed sharp emission lines at 4 K with a spectral width down to the spectral resolution limit of the experimental setup of 0.17 meV. This growth concept is discussed in comparison with conventional growth methods. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]