Cross-sectional transmission electron microscopy was used to observe the behavior of threading dislocations in a heterostructural GaN/AlGaN layer grown onto IL-AlN/GaN/LT-GaN/-Al2O3(00•1), where the IL-AlN and LT-GaN were an intermediate layer of AlN and a low-temperature buffer layer of GaN, respectively. Threading dislocations of a+c type, or threading dislocations with a Burgers vector of a+c, were formed at the low-temperature GaN layer and propagated upwards as far as the top surface; penetrating the AlGaN layer. A number of a-type threading dislocations were generated at the intermediate layer, and many of these were annihilated by about 100nm from the GaN/AlGaN interface. Rapid stress relief in the GaN layer on AlGaN was attributed to the annihilation of a-type threading dislocations.

Annihilation of Threading Dislocations in GaN/AlGaN. N.Kuwano, T.Tsuruda, Y.Adachi, S.Terao, S.Kamiyama, H.Amano, I.Akasaki: Physica Status Solidi A, 2002, 192[2], 366-70