Abrupt degradation of three types of semiconductor light emitting diodes at high temperature

Abstract

Abrupt degradation of three types of semiconductor light emitting diodes (LED’s), Ga_1−xAl_xAs double‐heterostructure (DH) LED’s, Ga_1−xAl_xAs/ GaAs DH LED’s, and LED‐operated Ga_1−xAl_xAs/ GaAs DH lasers operated at high temperature, was studied by electroluminescence topography, photoluminescence topography, and transmission electron microscopy. The following results were obtained from all types of the diodes. Dark regions which included 〈100〉 dark‐line defects (DLD’s) and/or 〈110〉 DLD’s were often observed in the electronluminescence or photoluminescence patterns of the active regions. Two phenomena were associated with this type of degradation as follows: (i) generation of high density of dislocations and dislocation loops (in some cases, stacking faults) by dislocation glide motion due to the relaxation of the stress concentrated in the active region. (ii) subsequent development of dislocation dipoles from the glided dislocations (often accompanied with many small dislocation loops). In some of the degraded diodes, the phenomenon (ii) did not occur. There might be a certain threshold for the phenomenon (ii).