Conventional and high resolution transmission electron microscopy were used to characterize GaN/AlN systems grown on sapphire (00•1) by plasma assisted molecular beam epitaxy. The filtering of threading dislocations was analyzed by using single and multiple thin high temperature AlN interlayers between high temperature GaN layers. A reduction of threading dislocation density was obtained comparing the measured values in samples with one and with three AlN interlayers. The dislocation interaction likelihood increased when the GaN layer between AlN interlayers was thicker.

Filtering Study of Threading Dislocations in AlN Buffered MBE GaN/Sapphire using Single and Multiple High Temperature AlN Intermediate Layers. A.Ponce, A.M.Sánchez, S.I.Molina, F.Fedler, J.Stemmer, J.Graul: Physica Status Solidi A, 2002, 192[2], 424-9