Formation of optically induced catastrophic degradation lines in InGaAsP epilayers

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Abstract
The formation of optically induced catastrophic degradation lines (CDL’s) in (001) InGaAsP epitaxial layers has been investigated by transmission electron microscopy. It appears that CDL’s evolve as a result of the temperature-gradient-induced migration of liquid droplets. These droplets could form in pre-existing regions where nonradiative recombination during optical pumping is very high. Further, the propagation of droplets involves dissolution followed by rapid deposition. Consequently, the resulting microstructures are highly defective and consist of decorated dislocations, loops, and precipitates. These features could act as nonradiative recombination centers and thus degrade the material. CDL’s propagate only along the 〈110〉 direction which is common to the {111}In,Ga and (001) planes. In addition, the Burgers vector of dislocations constituting a CDL is parallel to the direction of its propagation. Arguments have been developed to rationalize these observations.