X-ray topographic study of dark-spot defects in GaAs-Ga1−xAlxAs double-heterostructure wafers

Dark-spot defects (DSD) in a GaAs-Ga1−xAlxAs double-heterostructure (DH) wafer are studied by x-ray topography. Such DSD’s are one of the primary sources of the dark-line defects (DLD) that cause rapid degradation of GaAs-Ga1−xAlxAs DH lasers. By using x-ray topography almost all DSD’s observed by photoluminescence topography are correlated with dislocations in a GaAs substrate. In addition, it is observed that some dislocations in the substrate are not sources of DSD’s when the dislocation axes are nearly parallel to the surface of the substrate.