Morphologie und Wachstumsmechanismus von AIN‐Einkristallen

Pastrňák, J.; Roskovcová, L.

doi:10.1002/pssb.19640070128

Cited by 46 publications

(11 citation statements)

References 14 publications

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“…Crystals grown at 2050 C were mainly in the form of sixsided prismatic needles 0.1-0.3 mm in diameter and 5-15 mm in length. Very few elongated plates 0.5-1.0 mm wide and 5-7 mm long having the particular appearance described in detail by Pastrnak and Roskovcova [10] were also found. All these crystals were transparent and almost colorless with light yellow tint.…”

Section: Growth Procedures and Resultsmentioning

confidence: 87%

Natural growth habit of bulk AlN crystals

Epelbaum

Seitz

Magerl

et al. 2004

Journal of Crystal Growth

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Section: Growth Procedures and Resultsmentioning

confidence: 87%

Natural growth habit of bulk AlN crystals

Epelbaum

Seitz

Magerl

et al. 2004

Journal of Crystal Growth

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“…The investigated Al x Ga 1-x N layers with 0 < x < 1 were grown with plasma-assisted MBE on (0001) sapphire and are about 1 µm thick [14,15]. The AlN samples were fabricated by a direct reaction of aluminum vapor with nitrogen at high temperatures (1900 °C) [16,17]. These whiskers are some 10 µm thick and up to 1 cm long.…”

Section: Experimental 21 Samplesmentioning

confidence: 99%

Lattice dynamics in GaN and AlN probed with first‐ and second‐order Raman spectroscopy

Haboeck

Siegle

Hoffmann

et al. 2003

phys. stat. sol. (c)

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We present a selection of our contributions to basic research on the lattice dynamical properties of group-III nitrides and their alloys. We used first-order Raman scattering to determine the zone-center phonons and their dependence on structural attributes such as stress, chemical composition, impurities, and doping. Results on the angular dispersion of the polar modes, strain distribution, coupled LO-phonon plasmon modes, multi-mode behavior in Al x Ga 1-x N, and the quantitative determination of the phase purity of cubic and hexagonal GaN are shown. Second-order Raman-scattering experiments on GaN and AlN provide information on the vibrational states throughout the entire Brillouin zone. Based on a comparison of experimental data and calculated phonon-dispersion curves we assigned the observed structures to particular phonon branches and points in the Brillouin zone. We also discuss the behavior of the optical modes under large hydrostatic pressure. 1 Introduction During the last decade group-III nitrides have been an object of increasing research because of their interesting physical properties such as an adjustable band gap (1.9 eV to 6.2 eV) by varying the composition of the alloys [1] and application as basic materials for optoelectronic devices working in the blue and ultraviolet spectral region [2][3][4]. In particular GaN and AlN can withstand high temperatures and have large piezoelectric constants which makes them suitable for applications in highfrequency devices, sensors and low-dimensional structures [5,6].Although basic information about group-III nitrides e.g. crystal-and band structure have been available for a decade several details still remained unclear. In the following review of our work we present results of first-and second-order Raman investigations on various GaN, AlN, and Al x Ga 1-x N samples and point out some remarkable details of the structural and optical properties of these materials.

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“…Needle-like crystals grown at temperatures below 2000 °C were investigated in this study systematically. Along six-sided prismatic needles and elongated plates described in our previous paper [4] as well as in early studies of AlN crystals of Taylor and Lenie [7] and Pastrnak and Roskovcova [8], we have found a big number of long needles grown in [1120] direction. Such crystals are triangular in crosssection and they are usually longer as [0001] needles reaching up to 40 mm, which was already a geometrical limit in our growth setup.…”

Section: Resultsmentioning

confidence: 82%

Development of natural habit of large free‐nucleated AlN single crystals

Epelbaum

Nagata²,

Bickermann

et al. 2007

Physica Status Solidi (b)

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Well-shaped freestanding crystals of aluminum nitride up to 25 mm in length have been grown in tungsten crucibles using physical vapor transport (PVT) method. The platelet crystals exhibit characteristic asymmetric habit with largest flat being a pseudo-facet build by alternating (101 0) facets. Pronounced true facets are Al-terminated (0001) and adjacent {101 2} facets, with one of them growing much larger than others. The analysis of formation history of freestanding AlN crystals made it possible to explain their habit, very unusual for wurtzite-type structure. Growth of freestanding AlN starts from a long needle formed along the [11 2 0] direction at lower temperature of 1900 -2000 °C and continues by needle expansion and thickening along mainly [0001] direction, leading to asymmetric platelet. In such geometry only one extended (101 2) facet can be developed.

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Morphologie und Wachstumsmechanismus von AIN‐Einkristallen

Cited by 46 publications

References 14 publications

Natural growth habit of bulk AlN crystals

Natural growth habit of bulk AlN crystals

Lattice dynamics in GaN and AlN probed with first‐ and second‐order Raman spectroscopy

Development of natural habit of large free‐nucleated AlN single crystals

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