Investigation of propagation and coalescence of threading screw and mixed dislocations in 4H-SiC crystals grown by the high-temperature gas source method

Abstract

Propagation of threading screw dislocations (TSDs) and mixed dislocations (TMDs) in 4H-SiC crystals grown by the high-temperature gas source method were investigated. Cross-sectional samples cut in the growth direction were prepared and X-ray transmission topography with a diffraction vector g = 0004¯ was performed to reveal the dislocation lines. The topography image revealed that some pairs of TSDs/TMDs extending in the growth direction approached each other and merged in the middle of the grown crystal. Direct observations by synchrotron X-ray section topography confirmed that a pair of TSD and TMD with opposing c-component Burgers vectors had merged and the c-components of the dislocations were annihilated during crystal growth. Some pairs of TSDs/TMDs, however, showed no coalescence, although they could be annihilated topologically. The mechanism behind the success and failure of TSD/TMD coalescence was also discussed.