Influence of AlN buffer layer on growth of AlGaN by HVPE

To the end of improvement of layer morphology and crystalline perfection of thick AlGaN layers grown by hydride vapor phase epitaxy (HVPE) as well as for the suppression of crystallite formation during growth, the impact of AlN buffer layer properties on AlGaN growth was investigated. While the surface morphology of 500nm thick AlN layer improves with higher V/III ratio toward 50 and lower growth temperatures of 1020 degrees C, its use as a buffer layer for thick AlGaN layers leads to strong degradation of AlGaN surface and even to formation of different crystallites during growth. Best surface morphology and crystalline perfection of thick AlGaN layers was observed for the growth on an AlN buffer layer with a higher crystal quality disregarding its 3D morphology and high surface roughness. Best results were achieved at medium V/III ratio of about 10-20 and AlN buffer growth temperature of 1060 degrees C. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim