CHARACTERIZATION OF LOW DEFECT DENSITY BLUE-GREEN LASERS

We have used a combination of techniques to characterize low defect de nsity (less than or equal to 10(5) cm(-2)) blue-green separate confine ment heterostructure lasers. The limits of lattice mismatch between th e substrate and quaternary cladding layers that result in a pseudomorp hic laser structure were determined by X-ray diffraction and transmiss ion electron microscopy to be less than or equal to 0.0015. The determ ination of defect density (stacking faults, threading dislocations, et c.) in the active layer was performed by optical imaging. Photolumines cence imaging is nicely suited for defect observation, because of the nonradiative transitions associated with the defects and can easily be performed over large areas. Propagation of defects during device oper ation (device degradation) was monitored in real time with optical ima ging. The degradation was observed to start at grown-in defect sites ( in the active layer) that emanate from [100] dark line defects. From t he direct observation of device degradation, a mechanism involving the creation of new defects from nonradiative recombination at existing d efects sites is proposed.