Observation of Threading Dislocations in Ammonothermal Gallium Nitride Single Crystal Using Synchrotron X-ray Topography

Abstract

Synchrotron monochromatic-beam x-ray topography observation has been performed on high-quality ammonothermal gallium nitride single crystal to evaluate threading dislocations (TD) in a nondestructive manner. Asymmetric diffractions with six equivalent g-vectors of 11–26, in addition to a symmetric diffraction with g = 0008, were applied to determine the Burgers vectors (b) of dislocations. It was found that pure edge-type TDs with ${\varvec b} = \left\langle {11 - 20} \right\rangle /3$ did not exist in the sample. A dominant proportion of TDs were of mixed type with ${\varvec b} = \left\langle {11 - 20} \right\rangle /3 + \left\langle {0001} \right\rangle$, i.e., so-called c + a dislocations. Pure 1c screw dislocations with ${\varvec b} = \left\langle {0001} \right\rangle$ and TDs with c-component larger than 1c were also observed.