Correlation between dislocations and luminescence in GaN

A GaN film grown on sapphire substrate by metalorganic chemical vapor deposition have been investigated by the plan-view TEM and CL. Direct evidence of dislocation being a non-radiative recombination center, have been provided. A bulk GaN grown by the sublimation method and a homoepitaxial GaN grown by hydride vapor phase epitaxy have also been investigated by TEM, the x-ray diffraction and PL. The results confirm that it is not the dislocations but the point defects that are responsible for the yellow luminescence of the grown GaN. It was found, in a cross- section TEM image of a GaN/Al 2 O 3 film, that there are many precipitates gathered around a mixed dislocation. The precipitates might be formed by the segregation of point defects around dislocations. The precipitates might be formed by the segregation of point defects around dislocations. Since most of the point defects in GaN seems to segregate around the dislocations, dislocations can reduce the local concentration of the point defects in the no dislocation region. In this case, the optical property of GaN might be improved by the existence of the dislocation.