Minimisation of spanning dislocations in the crystallisation of deep amorphous silicon wells through the alignment of volume edges with fast growth directions

Deep amorphous silicon wells were created in a crystalline substrate by MeV ion-implantation. The sides of the rectangular amorphous volume were aligned normal to fast growth directions. Upon heating at elevated temperatures crystallisation proceeded inwards at both lateral and vertical interfaces. The progress of the epitaxy and the number and nature of the secondary structures formed were investigated through both plan-view and cross-sectional transmission electron microscopy analyses. The number of spanning dislocations was significantly reduced in this aligned configuration compared with the situation where the sides of the well were not coincident with crystallographic directions. The reduction in the number of spanning dislocations allowed a more complete characterisation of other defects which arise uniquely from the crystallisation of volumes in this geometry.