Structural and spectroscopic properties of AlN layers grown by MOVPE

Abstract

The effects on surface morphology, crystal quality, and growth rate of undoped AlN layers grown on c-plane sapphire substrates due to the changes in growth parameters, such as V-III ratio, N 2 2H 2 ratio, and growth temperature in LP-MOVPE are studied here. The optimized growth process resulted in an almost flat surface morphology with a significantly reduced number of hexagonal pits ð3 Â 10 7 cm À2 Þ and good crystalline quality having a rms value of roughness of 0.4 nm measured by atomic force microscopy and a high resolution X-ray diffraction (HRXRD) FWHM value for (0 0 0 2) reflection of 200 arcsecs. The threading dislocation density of the AlN layer is estimated approx. 10 9 cm À2 from cross-sectional transmission electron microscopy (TEM) measurements. Additionally, these optimized samples show a strong donor-bound exciton luminescence signal with a FWHM of 20 meV. Furthermore, small period AlN/ GaN superlattice structures with excellent uniformity were grown, as proven by our HRXRD and TEM studies.

Influence of Conditions of Growth on Structural Perfection of Layers of Aln Received by Method Mos-Gidridnoy of an Epitaxy

“…Это может быть связано с образованием частиц AlN в газовой фазе вследствие паразитных реакций между TMAl и NH 3 . Известно [4], что такие реакции, вероятность проте-кания которых возрастает при относительно высоких отношениях V/III, способны существенно ухудшить кристаллическое совершенство и морфологию по-верхности формируемого слоя вследствие осаждения на ней образовавшихся в газовой фазе частиц AlN. Очевидно, использованное снижение отношения V/III оказалось недостаточным для заметного улучшения качества структуры образца.…”

“…Они ухудшают структурное совер-шенство материала и существенно снижают скорость роста [4]. Пред-ложен ряд подходов, позволяющих в той или иной степени устранить перечисленные выше недостатки [5][6][7].…”

“…Для исследований зависимости физико химических свойств металлоргани-ческих полимерных нанокомпозитов от технологических параметров их получения предлагается исполь-зовать QSPR (quantitative structure property relationship) модель [4,5] с применением метода наименьших…”

The influence of thickness and ammonia flow rate on the properties of AlN layers

“…Unfortunately, large lattice and thermal mismatches between AlN and sapphire lead to high dislocation densities in the epitaxial layers. On the other hand, the parasitic reactions between group-13 and group-15 precursors (also referred to as III and V), and the insufficient mobility of Al atoms are serious problems that need to be overcome for high-quality AlN growth, which deteriorate the structural and morphological quality of layers [4,5]. Therefore, researches have primarily focused on the growth of layers with an excellent crystalline quality and a smooth surface by various growth-techniques, -processes, and -parameters.…”

Low temperature growth of c-axis oriented AlN films on γ-LiAlO2 by radio frequency magnetron sputtering

“…[3][4][5]. AlN films can be grown on sapphire by metal organic chemical vapor deposition [6,7] or molecular beam epitaxy [8][9][10] at high growth temperature. The crystalline quality of AlN films is deteriorated by threading dislocations which usually originate from the large lattice mismatch and * Corresponding author.…”