Annihilation of Threading Dislocations in GaN/AlGaN

Abstract

Cross‐sectional transmission electron microscopy (TEM) was performed to observe the behavior of threading dislocations (TDs) in a heterostructure of a GaN/AlGaN layer grown on IL‐AlN/GaN/LT‐GaN/α‐Al2O3(0001), where IL‐AlN and LT‐GaN are an intermediate layer of AlN and a low‐temperature buffer layer of GaN, respectively. TDs of ( a + c)‐type, or TDs with a Burgers vector a + c, are formed at the LT‐GaN layer and propagate upwards as far as the top surface, penetrating the AlGaN layer. A number of a‐type TDs are generated at the IL, and many of these are annihilated within about 100 nm above the GaN/AlGaN interface. Quick stress relief in the GaN layer on AlGaN is due to the annihilation of a‐type TDs.

Dislocation reactions in hetero‐epitaxial (0001) GaN layers

“…In this case, the line direction of the a dislocation on the right was initially horizontal and it bent slightly vertically toward the left one. Similar annihilation reactions between a dislocations have been observed at GaN/AlGaN interfaces before [19]. At location (3), two c dislocations with opposite signs of Burgers vectors annihilated.…”

Flat (1120) GaN Thin Film on Precisely Offset-Controlled (1102) Sapphire Substrate

“…A similar phenomenon was observed on the growth of c-axis oriented GaN on AlGaN. 10,11) The roughening of the surface and the formation of a small inclined facet at the initial stage of GaN growth on the AlGaN interlayer are thought to be the cause of the bending and annihilation of dislocations. The reason for the bending of dislocations is the self-induced strain field around the dislocations.…”

Intersubband absorption properties of high Al content Al x Ga1−xN/GaN multiple quantum wells grown with different interlayers by metal organic chemical vapor deposition

“…Anomalously, the value of FWHM corresponding to MQW films with interlayers is larger than that of the GaN templates. When the interlayer was inserted, the FWHM increased, which seems to contradict the similar result of the traditional scheme [21,22]. Usually, the interlayer blocks the threading dislocation that originated from the GaN template, leading to the decrease of the FWHM of the subsequent film.…”