Reduction of threading dislocation densities in AlN∕sapphire epilayers driven by growth mode modification

摘要: A strategy to reduce the density of threading dislocations (TDs) in AlN epilayers grown on sapphire substrates is reported. The TDs experience a redirection their line orientation which found coincide with imposed increases both V/III ratio and overall flux rate leading formation an internal subinterface delineated by changes dislocation orientation. Threading either large kinks then redirect into or form dipole half loops via annihilation redirected segments opposite sign latter significant reduction. These phenomena can be accounted for transition growth mode from atomic step flow two-dimensional layer-by-layer accompanies flux. As this occurs, macrosteps (several layers thick) laterally overgrow pre-existing outcrops. Image forces initiate processes create trailing parallel interface between advancing macrostep surface outcrop. This horizontal segment forced should another traveling direction encountered. again nucleate replicated as crystal grows. loop will if two are so meet each other.