High-temperature AlN interlayer for crack-free AlGaN growth on GaN

This paper presents a study of the transformation of high-temperature AlN (HT-AlN) interlayer (IL) and its effect on the strain relaxation of Al0.25Ga0.75N/HT-AlN/GaN. The HT-AlN IL capped with Al0.25Ga0.75N transforms into AlGaN IL in which the Al composition increases with the HT-AlN IL thickness while the total Ga content keeps nearly constant. During the HT-AlN IL growth on GaN, the tensile stress is relieved through the formation of V trenches. The filling up of the V trenches by the subsequent Al0.25Ga0.75N growth is identified as the Ga source for the IL transformation, whose effect is very different from a direct growth of HT-AlGaN IL. The a-type dislocations generated during the advancement of V trenches and their filling up propagate into the Al0.25Ga0.75N overlayer. The a-type dislocation density increases dramatically with the IL thickness, which greatly enhances the strain relaxation of Al0.25Ga0.75N. (c) 2008 American Institute of Physics.

National Natural Science Foundation of China 60476021 69825107Fund for Scientific Research, Flanders (FWO) Concerted Action of the KULeuven GOA/2004/02 Inter-university Attraction Pole IUAPP6/42 Center of Excellence Programme INPAC EF/05/005 Bilateral Cooperation between Flanders and China BIL 07/03 This work was supported by the National Natural Science Foundation of China (Grant Nos. 60476021 and 69825107). the Fund for Scientific Research, Flanders (FWO), the Concerted Action of the KULeuven (GOA/2004/02), the Inter-university Attraction Pole (IUAPP6/42), the Center of Excellence Programme (INPAC EF/05/005), and the Bilateral Cooperation between Flanders and China (BIL 07/03).