Characterization of Threading Dislocations in PVT-Grown AlN Substrates via x-Ray Topography and Ray Tracing Simulation

Abstract

Threading dislocations in aluminum nitride boules grown by physical vapor transport method were systematically studied via synchrotron x-ray topography (white beam and monochromatic) in conjunction with ray tracing simulations. Two major types of threading dislocations were observed in the c-axis-grown boules: threading screw dislocations (TSDs) and threading edge dislocations (TEDs) with Burgers vectors along the [0001] and \(\langle 11\bar{2}0 \rangle \) directions, respectively. TSDs were typically observed in the middle of the boule while TEDs were commonly observed to aggregate into arrays along the \( \langle 1\bar{1}00 \rangle \) and \( \langle 11\bar{2}0 \rangle \) directions in various parts of the boule on basal plane oriented wafers. By comparison with ray tracing simulations, the absolute Burgers vectors of both TSDs and TEDs in the arrays could be unambiguously determined. TEDs comprise over 90 % of all threading dislocations observed. The relationships between TED arrays and low angle grain boundaries and their possible formation mechanisms are discussed.