Evidence of relationship between strain and In-incorporation: Growth of N-polar In-rich InAlN buffer layer by OMCVD

CHAUHAN, Prerna – HASENÖHRL, Stanislav – DOBROČKA, Edmund – CHAUVAT, Marie-Pierre – MINJ, A. – GUCMANN, Filip – VANČO, Ľubomír – KOVÁČ, Jaroslav jr. – KRET, S. – RUTERANA, Pierre – KUBALL, Martin – ŠIFFALOVIČ, Peter – KUZMÍK, Ján

In Journal of Applied Physics. 125, iss. 10 (2019)



Two In𝑥Al1−𝑥NInAl1−N layers were grown simultaneously on different substrates [sapphire (0001) and the Ga-polar GaN template], but under the same reactor conditions, they were employed to investigate the mechanism of strain-driven compositional evolution. The resulting layers on different substrates exhibit different polarities and the layer grown on sapphire is N-polar. Moreover, for the two substrates, the difference in the degree of relaxation of the grown layers was almost 100%, leading to a large In-molar fraction difference of 0.32. Incorporation of In in In𝑥Al1−𝑥NInAl1−N layers was found to be significantly influenced by the strain imposed by the under-layers. With the evolutionary process of In-incorporation during subsequent layer growth along [0001], the direction of growth was investigated in detail by Auger electron spectroscopy. It is discovered that the In0.60Al0.40NIn0.60Al0.40N layer grown directly on sapphire consists of two different regions with different molar fractions: the transition region and the uniform region. According to the detailed cross-sectional transmission electron microscopy, the transition region is formed near the hetero-interface due to the partial strain release caused by the generation of misfit-dislocations. The magnitude of residual strain in the uniform region decides the In-molar fraction. In𝑥Al1−𝑥NInAl1−N layers were analyzed by structural and optical characterization techniques. Our present work also shows that a multi-characterization approach to study In𝑥Al1−𝑥NInAl1−N is a prerequisite for their applications as a buffer layer.