Nature of dark defects revealed in InGaAsP/InP double heterostructure light emitting diodes aged at room temperature

Abstract

The nature of the dark defects which have appeared in the InGaAsP/InP double heterostructure light emitting diodes aged at room temperature were studied by transmission electron microscopy and other related methods. According to the observation of many diodes by electroluminescence topography, the dark defects were classified into five types: cross-hatched 〈110〉 dark line defects, regular tetragonal 〈110〉 dark line defects, regularly distributed dark spot defects, dark band defects, and dark spot defects whose circumference was bright. These dark defects corresponded to misfit dislocations, stacking faults which originated from the interface between the epitaxial layer and the substrate, precipitate-like spherical defects, mechanical damages induced during epitaxial growth, and alloyed regions produced by the penetration of the electrode metals, respectively. It was found that both the dislocation glide process and the dislocation climb motion due to the nonradiative recombination of the minority carriers which have been often observed in the GaAlAs/GaAs double heterostructure materials occurred only with difficulty in the InGaAsP/InP double heterostructure materials. These phenomena could be well explained by the difference between these materials in term of interaction between impurity atoms and dislocations and/or the electronic state of defects and nonradiative recombination rate at defects.