The Effect of AlN Nucleation Temperature on the Growth of AlN Films via Metalorganic Chemical Vapor Deposition

Abstract

AlN epilayers were grown directly on sapphire (0001) substrates using a combined growth scheme, consisting of a low-temperature nucleation layer and a second layer grown by high-temperature pulsed atomic layer epitaxy via metalorganic chemical vapor deposition. With an emphasis on the nucleation layer, its growth temperature was varied from 470°C to 870°C, and obvious differences in the surface morphology, crystal quality, and strain states of the overall AlN epilayers were observed. Based on atomic force microscopy, x-ray diffraction, and Raman spectroscopy results, these differences are ascribed to the nucleation sites and the subsequent grain size. Due to the enhanced mobility of Al adatoms with increasing temperature, the nucleation sites decrease and the subsequent grain size increases, leading to the achievement of atomically flat AlN epilayers with good crystal quality for the nucleation layer grown at 570°C. However, at higher nucleation layer growth temperature, the properties of the AlN epilayers deteriorate due to the possible appearance of misaligned AlN grains. A model is also developed according to all observations.

Investigation on HT-AlN Nucleation Layers and AlGaN Epifilms Inserting LT-AlN Nucleation Layer on C-Plane Sapphire Substrate

“…In order to study further the influence on the crystal Ref. [19] studied the size of AlN island under different growth temperature modes, as can be seen from Fig. 6, the size of AlN islands grown under low-temperature mode is smaller than the size of those grown under intermediate temperature and high temperature [19], which coincides with AFM images results.…”

Influence of initial growth stages on AlN epilayers grown by metal organic chemical vapor deposition

“…AlN with Al polarity has been found to exhibit a smoother surface while AlN with mixed polarity (Al and N) has a rougher surface morphology [11][12][13]. On the other hand, precursors flow prior to the deposition of the NLs [9], thickness of the NLs, the density and the size of the nucleation islands (NIs) have been found to influence the quality of the AlN layers [14][15][16][17]. Nevertheless, studies on the initial stages of AlN growth are still scarce, when compared to GaN.…”

Centimeter-Transferable III-Nitride Membrane Enabled by Interfacial Adhesion Control for a Flexible Photosensitive Device

“…It is reported that the Al adatoms on bare sapphire have higher mobility as the growth temperature increases; then, they could move to the sites with lower nucleation formation energy and tend to be a large nuclei size. 36,37 According to our early work, the migration barrier (0.07 eV) of the Al atom on graphene is lower than that of sapphire (0.21 eV), 31 and AlN prefers to nucleate at the wrinkles and broken boundaries of graphene, in which the N atoms doping easily happens, then, providing a lower Al absorption energy. 38 For the lowest temperature of 950 °C, the insufficient mobility of Al adatoms results in higher normal growth rate than that of the lateral; thus, numerous AlN nuclei generate.…”