Morphological features related to micropipe closing in 4H-SiC -: art. no. 034905

The closing of micropipes during sublimation epitaxy has been studied. Shallow trenches are formed along the direction of the step-flow growth in the vicinity of closed micropipes. The trenches are related to a serious disturbance of the flowing steps and the formation of stacking faults in the (0001) basal plane as well as in the (1 (1) over bar 00) plane. A micropipe closes when the speed of the growth steps is higher than the spiral growth around the micropipe. This mechanism is related to a bending of the micropipe along the trench and the progressive emission of elementary screw dislocations along the trench. The morphology of the disturbed steps at the trenches and the related defects have been studied by transmission electron microscopy and atomic force microscopy. Supporting evidences are presented with optical micrographs from etched epilayers. Image forces, which are developed by the growth steps, stabilize the bending of the micropipes. The limitation of the bending is also discussed. (c) 2005 American Institute of Physics.