DEFECT STRUCTURE OF DEGRADED GA1-XALXAS DOUBLE-HETEROSTRUCTURE LIGHT-EMITTING-DIODES

The defect structure of degraded Ga1-xAlxAs double-heterostructure (DH) light-emitting diodes (LED's) was investigated by electroluminescence (EL) topography and transmission electron microscopy (TEM). Two types of dark-line defects (DLD's), 〈100〉 DLD's and 〈110〉 DLD's, and dark-spot defects (DSD's) were observed in EL patterns of degraded LED's. Dislocation dipoles or large zigzag-shaped dislocation loops were associated with DSD's and 〈100〉 DLD's. The dipoles had Burgers vectors of the type (a/2) 〈011〉 inclined at 45° to the (001) junction plane or (a/2) 〈110〉 parallel to the junction plane and were extrinsic in character. The zigzag-shaped dislocation loops had Burgers vectors of the type (a/2) 〈011〉 and were extrinsic in character. On the other hand, multiple stacking faults which lay in 〈110〉 directions or half dislocation loops which also lay in 〈110〉 directions and had Burgers vectors of the type (a/2) 〈011〉 inclined at 45° to the junction plane or (a/2) 〈110〉 parallel to the junction plane were associated with 〈110〉 DLD's.