CATASTROPHIC DAMAGE OF ALXGA1-XAS DOUBLE-HETEROSTRUCTURE LASER MATERIAL

We carry out a detailed study of catastrophic degradation (CD) in DH laser material from which we reach two conclusions. First, local melting occurs and is due to intense nonradiative recombination of minority carriers at a cleaved surface or at a defect. The minority carriers are generated by absorbed superradiant light. Second, the dark line associated with CD results from propagation of a molten zone confined to the active layer. It is recrystallized epitaxially after the laser pulse but remains highly nonradiative because large numbers of point defects and dislocation loops are quenched into this region during rapid cooling from the molten state. Catastrophic damage was induced by exciting superradiance in the DH material with a cavity-dumped Ar-ion laser. The melting and recrystallization were established by observing a redistribution of Ga and Al in the x=0.08 active layers by TEM studies. The point defects were detected by scanning junction photocurrent measurements, electron-beam-induced current, and cathodoluminescent analysis. Calculations of the power required for thermal runaway at a cleaved surface, melting, and propagation of a molten zone are within twice the observed threshold intensities.