Cross-sectional transmission electron microscopy was performed to observe the behavior of threading dislocations in a heterostructure of a GaN/AlGaN layer grown on IL-AlN/GaN/LT-GaN/α-Al2O3(0001), where 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 a+c, were formed at the LT-GaN layer and propagate upwards as far as the top surface, penetrating the AlGaN layer. A number of a-type threading dislocations were generated at the IL, and many of these were annihilated within about 100nm above the GaN/AlGaN interface. Quick stress relief in the GaN layer on AlGaN was due 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