Influence of growth temperature on intrinsic stress distribution in aluminum nitride grown by hydride vapor phase epitaxy
Controlling stress is a fundamental issue in thin film growth, and this problem becomes more complicated in AlN film growth due to low mobility of Al adatoms. To study the evolution of intrinsic stress distribution in the beginning of growth as a function of growth temperature, AlN films were grown directly on sapphire (0001) substrates at three different growth temperatures by hydride vapor phase epitaxy (HVPE). Transmission electron microscopy (TEM) demonstrated that the intrinsic stress distribution is periodic and the period increases with the increase of temperature. At lower growth temperature, the intrinsic stresses overlap with the dislocations during the initial growth, appearing as periodic nano-sized columns perpendicular to the AlN/sapphire interface when the sample is viewed with g = 112¯0. In addition, the period is different along [11¯00] and [112¯0] for a certain temperature. With the increase of growth temperature, a large fraction of misfit dislocations bend and terminate at around 1.5 μm above the interface of AlN/sapphire forming a network. The periodicity of the stress distribution is thought to originate due to different mobilities of Al adatoms. This understanding helps to achieve stress-controllable AlN growth.
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Document Type: Commentary
Publication date: August 1, 2016
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