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1

On GaN Crystallization by Ammonothermal Method

100%

Dwiliński R., Baranowski J., Kamińska M., Doradziński R., Garczyński J., Sierzputowski L.

Acta Physica Polonica A

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1996

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vol. 90

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issue 4

763-766

EN

GaN crystals are grown using ammonothermal method at pressures below 5 kbar and temperatures below 550°C. In this method, GaN is synthesised from high purity metallic gallium. The main role in the low temperature GaN crystallization is played by the chemically active and dense ammonia and dissolved mineralizer. Morphology of the obtained crystals as well as solubility experiments prove that gallium nitride is dissolved and crystallised from solution. Physical properties of GaN crystals obtained using ammonothermal method depend on the growth conditions and the type of mineralizer. All GaN samples reveal very intensive photoluminescence, also at room temperature. The spectra of crystals grown with lithium compound mineralizer are shifted towards higher energies in comparison to crystals grown with potassium based mineralizer. At helium temperatures, phosphorescence is also observed.

2

Some Optical and Epr Properties of Strain-Free GaN Crystals Obtained by Ammono Method

100%

Dwiliński R., Baranowski J. M., Kamińska M., Doradziński R., Garczyński J., Sierzputowski L., Palczewska M.

Acta Physica Polonica A

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1997

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vol. 92

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issue 4

737-741

EN

AMMONO GaN is grown spontaneously from ammonia solution in form of regular, well shaped, few micrometer crystals. Photoluminescence spectra of these crystals are characterized by fixed positions of very narrow exciton lines (FWHM down to 1 meV), where free excitons A, B, C, resolved two donor bound excitons and acceptor bound exciton are visible. Fixed position of exciton lines is in contrast to small changes of line energies which have been always observed for epitaxial GaN layers because of strain present in them. Free electron concentration of AMMONO GaN is less than few times 10^{15} cm^{-3}, as estimated from EPR signal of shallow donor. The above-mentioned facts qualified these crystals as state of the art strain-free, model material for basic parameter measurements of GaN. In this work, results of PL and EPR measurements performed on AMMONO GaN crystals are presented and discussed.

3

GaN Synthesis by Ammonothermal Method

84%

Dwiliński R., Wysmołek A., Baranowski J., Kamińska M., Doradziński R., Garczyński J., Sierzputowski L., Jacobs H.

Acta Physica Polonica A

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1995

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vol. 88

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issue 5

833-836

EN

It is shown that ammonothermal method can be successfully used to synthesize GaN powder of good crystallographic quality from ammonia solution at high pressure and a moderate temperature. The size of obtained GaN powder grains was of a few micrometers. The improvement of the powder crystalline quality (examined by X-ray rocking curve, scanning electron microscopy and luminescence measurements) with increasing molar proportion of mineralizer was observed. It was therefore possible to conclude that high molar proportion of mineralizer in ammonia solution plays a crucial role in the polycrystal growth process. Visible luminescence of high efficiency from the GaN powder was found.

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3 Acta Physica Polonica A

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3 Garczyński J.

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2 Baranowski J.

1 Baranowski J. M.

1 Jacobs H.

1 Palczewska M.

1 Wysmołek A.

On GaN Crystallization by Ammonothermal Method

Some Optical and Epr Properties of Strain-Free GaN Crystals Obtained by Ammono Method

GaN Synthesis by Ammonothermal Method