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Free-standing HVPE-GaN Layers
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
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2003 (English)In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 0, no 7, 1985-1988 p.Article in journal (Refereed) Published
Abstract [en]

We have grown GaN layers with a thickness up to 340 μm in an rf-heated vertical HVPE reactor with a bottom-fed design. The GaN layers were separated from the sapphire substrate by a LLO process. The free-standing GaN was investigated by HRXRD, AFM and low temperature CL. The FWHM values of the ω-scans are 96 and 129 arcsec for the (104) and (002) reflection, respectively, which indicates high crystalline quality. The c and a lattice parameters are determined as c = 0.51850 ± 0.00004 nm and a = 0.31890 ± 0.00004 nm, indicating stress free material. The etch pit density was estimated to be 1 × 107 cm−2. The used HVPE growth procedure together with the subsequent LLO are obviously capable to provide high-quality free-standing GaN material for further epitaxial overgrowth.

Place, publisher, year, edition, pages
2003. Vol. 0, no 7, 1985-1988 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-85826DOI: 10.1002/pssc.200303333OAI: oai:DiVA.org:liu-85826DiVA: diva2:572960
Available from: 2012-11-29 Created: 2012-11-29 Last updated: 2017-12-07
In thesis
1. Growth of thick GaN layers on sapphire by Hydride Vapour Phase Epitaxy
Open this publication in new window or tab >>Growth of thick GaN layers on sapphire by Hydride Vapour Phase Epitaxy
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Gallium nitride (GaN) is a wide bandgap material that is already extensively used in industrial production of optoelectronic devices (light emitters) that operate in the blue and ultraviolet wavelength range. GaN is interesting not only because it has a wide bandgap (3.5 eV), it is also chemically and physically inert and is environmental friendly for device production, as opposed to the lower bandgap III-V materials based on GaAs or InP.

Despite recent efforts there is still no bulk GaN substrates with sufficient crystal quality and size and sufficiently low price that they can be used commercially in devices. The problem in growing GaN is that because there are no native substrates the growth is done on foreign substrates (heteroepitaxy). When GaN is grown heteroepitaxially there will be a built in strain in the material because of the lattice mismatch and thermal expansion difference between the materials. This produces a number of different defects that degrades the crystal quality. Native GaN substrates are therefore strongly in demand, and many growth techniques are presently pursued worldwide to develop such substrates.

Hydride Vapor Phase Epitaxy (HVPE) is the growth technique most commonly used for growing bulk GaN material. Certainly it is the most developed method, and it can produce a high growth rate(> 100 μ/hr). HVPE has comparatively simple growth chemistry and is relatively economic compared to other growth techniques.

In the work involved in this PhD thesis the focus has been to optimize the growth of thick 2" diameter GaN layers on sapphire with a vertical HVPE system.

Paper I deal with how to grow thick GaN layers(> 300 μm) on sapphire, and reviews some of the problems that are involved in the growth process. The emphasis is on the growth related defects in such thick GaN layers.

In Paper II we have shown that it is possible to grow GaN with a very high growth rate and with good crystal quality.

Paper III shows that it is possible to produce a free-standing GaN layer that is strain free. This is done by separating the GaN layer from the sapphire substrate using a laser lift-off (LLO) process.

In paper IV the optical and structural properties of thick freestanding GaN layers are reported.

In paper V we have shown that it is possible to grow a GaN layer on sapphire over a 2" area that is virtually strain free over most part of the grown area. This is due to induced cracking in the starting sapphire substrate during the cool down phase.

In paper VI we have grown the GaN material on a starting template consisting of a two-step epitaxial lateral overgrowth (ELO) GaN layer grown by MOVPE on a sapphire substrate. The self separated GaN layer was then evaluated and the result showed a virtually strain free material.

In paper VII positron annihilation studies of a thick GaN layer is performed. The studies were done to identify native point defects (Ga vacancies) in the as-grown non-intentionally doped n-type GaN.

Paper VIII deals with μ-Raman scattering profiling studies on a thick free-standing GaN layer. The studies provided the vertical strain distribution and the evolution of the crystalline quality with increasing layer thickness.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2005. 45 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 958
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-31201 (URN)16949 (Local ID)91-85299-75-8 (ISBN)16949 (Archive number)16949 (OAI)
Public defence
2005-06-15, Hörsal Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-11-29

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Larsson, HenrikGogova, DanielaYakimova, RositsaMonemar, Bo

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