Sublimation growth of AlN bulk crystals in Ta crucibles

Мохов, Е. Н.; Avdeev, O.V.; Barash, I. S.; Chemekova, T. Yu.; Роенков, А. Д.; Segal, A.S.; Wolfson, Albert; Makarov, Yu.N.; Ramm, M.G.; Helava, H.

doi:10.1016/j.jcrysgro.2005.03.016

Cited by 104 publications

(107 citation statements)

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“…[4][5][6][7] These applications in turn triggered improvements in the growth of high-quality AlN, [8][9][10] only recently allowing us to investigate the fundamental properties of this semiconductor in unpreceded quality. For example, the full width at half maximum of donor bound-exciton recombinations in AlN could be shown to be below 500 μeV, allowing for unambiguous identification of these lines, 11,12 or the optical properties of nonpolar quantum wells in AlN barriers could be understood.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic absorption and emission of bulk(11¯00)AlN

et al. 2013

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The intrinsic anisotropic optical properties of wurtzite AlN are investigated in absorption and emission. Full access to the anisotropy of the optical response of the hexagonal material is obtained by investigating the (1100) plane of a high-quality bulk crystal allowing electric field E polarization perpendicular (E ⊥ c) and parallel (E c) to the optical axis c. Spectroscopic ellipsometry yields the ordinary (ε ⊥ ) and extraordinary (ε ) dielectric functions (DFs) from 0.58 up to 20 eV. The comparison of the experimental data with recently calculated DFs demonstrates that Coulomb interaction has a strong impact not only on the spectral dependence around the fundamental absorption edge but also on the high-energy features usually discussed in terms of van Hove singularities. The fits of the second-order derivatives of ε and ε ⊥ provide the transition energies for the main features in this range. The DFs close to the fundamental absorption edge, dominated by free excitons, exciton-phonon complexes, and the exciton continuum, are independently confirmed by reflectivity and synchrotron-based photoluminescence excitation studies. Values for the band gaps, the crystal field ( cf = −221 ± 2 meV), and spin-orbit splittings ( so = 13 ± 2 meV) are obtained. Furthermore, we obtain accurate values for the static dielectric constants of ε S⊥ = 7.65 and ε S = 9.21, entering, e.g., the calculations of exciton binding energies. Photoluminescence is used to investigate the emission properties of the same sample.

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Section: Introductionmentioning

confidence: 99%

Anisotropic absorption and emission of bulk(11¯00)AlN

et al. 2013

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“…[1][2][3][4][5] Aluminum nitride has the same crystal structure (i.e. wurtzite) as all compositions of Al x Ga 1-x N, thus epitaxy in any crystal orientation should be possible on AlN.…”

Section: Introductionmentioning

confidence: 99%

“…3,4,8 This method is based on driving the reaction AlN(s) = Al(v) + ½N 2 forward in the source zone and in reverse in the crystal growth zone. The source is typically AlN powder or a sintered polycrystal, and sublimation occurs at temperatures greater than 1900 °C.…”

Section: Introductionmentioning

confidence: 99%

“…17 Oxidation occurs in the presence of oxygen; hydroxidation occurs when aluminum oxides react with water vapor in air. The amorphous thin film that forms may be a mixture of one or several aluminum-oxygen-hydrogen compounds such as aluminum trihydroxide (Al(OH) 3 ), aluminum oxide hydroxide (AlOOH, or Al 2 O 3 ·H 2 O), or aluminum oxide (Al 2 O 3 ). 18 The Gibbs free energy of formation of these compounds at room temperature have large negative values, so there is a strong tendency for them to form.…”

Section: Introductionmentioning

confidence: 99%

“…If the oxygen is present as AlOOH or Al(OH) 3 , reactions involving hydrogen may also be effective at removing oxygen from AlN powder via the formation of water. In this case, the reactions might involve (1) 2Al(OH) 3 25 supports the probability of reactions 1 and 2 occurring.…”

Section: Introductionmentioning

confidence: 99%

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Native oxide and hydroxides and their implications for bulk AlN crystal growth

Edgar

Nyakiti

et al. 2008

Journal of Crystal Growth

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Oxygen degrades the properties of AlN, thus producing bulk single crystals with low oxygen concentrations is an important goal. Most of the oxygen in bulk AlN single crystals grown by the sublimation-recondensation method originates from the hydroxides and oxides that spontaneously form on the surfaces of the AlN source powder. For a typical AlN powder with an average particle size of 1-2 microns, a 1-3 nm thick oxide and/or hydroxide can account for most of its oxygen (generally on the order of 1.0 wt%) and hydrogen (200-300 ppm). Heating the AlN powder source at 1950 °C for 10 h in a nitrogen atmosphere reduced its surface area by a factor of 160 (due to sintering), the oxygen concentration by 16, and the hydrogen concentration by 67. The difference in these reduction factors suggests some of the oxygen is dissolved into the bulk AlN with this heat treatment. By first annealing the AlN powder at a low temperature (950-1000 °C) for several hours before sintering at 1950 °C, the oxygen and hydrogen concentrations were reduced to lower levels. The low temperature treatment is effective eliminating oxygen and hydrogen from the surface of the powder, while high temperature sintering reduces the specific surface area of the source. The combination of heat treatments produced a source with oxygen and hydrogen concentrations as low as 0.015 wt% O (1.9 x 10 19 atoms O cm -3 ) and 1.7 ppm H (3.4 x 10 18 atoms H cm -3 ). Annealing becomes less effective at removing oxygen and hydrogen with longer heat treatments, suggesting there is a minimum oxygen concentration that can be produced with this method.

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