Analysis of dislocation line tilt in GaN single crystal by Raman spectroscopy

The strain field of the tilted threading dislocation (TD) in a hydride vapor-phase epitaxy-grown c-plane (0001) GaN single crystal is demonstrated using Raman spectroscopy. In the two-dimensional mapping image of the E-2(H) peak shift around TDs, high-contrast areas corresponding to pairs of high and low wavenumber regions of the peak shift are observed, and the edge component of the Burgers vector can be specified. Deformed contrast areas extending in the specified direction are also observed. This deformed contrast region indicates tilted dislocations since 2D mapping also detects strain deep below the surface due to the transmission of the laser beam. Simulation of the E-2(H) peak shift mapping around the TD, tilted at 0 degrees and 60 degrees in the [11 (2) over bar0] direction and having a Burgers vector b = 1/ 3[11 (2) over bar0], is also performed. The simulation of the 60 degrees tilted dislocation shows that the contrast extends in one direction. The line profiles of the E-2(H) peak shift by simulation are in agreement with the experimental results. We propose that the dislocation line tilt can be analyzed from the 2D Raman mapping images. (c) 2020 The Japan Society of Applied Physics

Automated summary

Raman spectroscopy was used to demonstrate the strain field of tilted threading dislocations in a c-plane GaN single crystal grown by hydride vapor-phase epitaxy. The high-contrast areas and deformed contrast regions observed in the 2D mapping images provide insights into the Burgers vector edge component and tilted dislocations. Simulation results showed that a 60-degree tilted dislocation exhibited contrast extending in one direction, consistent with experimental line profiles of the E-2(H) peak shift.