DEFECT MECHANISMS IN DEGRADATION OF INGAASP LONG-WAVELENGTH EDGE-EMITTING LIGHT-EMITTING-DIODES

We report on degradation mechanisms in 1.3-mu-m wavelength edge-emitting light-emitting diodes aged for 1000 h at 150-degrees-C and 150 mA studied by transmission electron microscopy. During this degradation, three types of defect structures are generated at the interface between InGaAsP active layer and n-InP buffer layer along the light emitting stripe: (i) 1/2<100> {100} faulted extrinsic dislocation loops formed by condensation of point defects, similar to those previously observed in degraded channeled substrate buried heterostructure lasers, (ii long 1/2<101> dislocation clusters developed along the active stripe, and (iii) 1/3[111] and 1/3[11BAR1] faulted Frank loops developed from condensation of point defects onto the 1/2[101] dislocation through dissociative reactions: 1/2[101]--> 1/6[12BAR1] + 1/3[111] and 1/2[101] --> 1/6[121] + 1/3[11BAR1]. The driving force for these reactions is discussed.