Degradation of InGaAsP/InP-based multiquantum-well lasers

The formation of dark-area defects (DADs) along the active stripe in InGaAsP/InP-based buried-heterostructure multiquantum-well (BH-MQW) lasers, observed in electroluminescence and photoluminescence (PL) after degradation, is found to be related to dislocations along [011]. The fact that DADs only occurred in lasers showing an increase in threshold current of more than 30% indicates that the [011] dislocations are a consequence rather than the actual origin of the degradation. Observed jogs along a [011] dislocation imply the presence of point defects in the active stripe. The nature of these point defects is not clear, but a comparison of the results for lasers with p/n and semi-insulating current blocking singles out Zn as being a possible candidate. An observed direct proportionality between the increase in threshold current and the reduction in PL intensity is interpreted as being due to a reduction in carrier lifetime due to enhanced nonradiative recombination. A dependence of the distribution of threshold-current increase on current density during aging is explained in terms of a model, in which nonradiative defects are generated during current injection. A comparison of the degradation in MQW and in bulk lasers without an MQW structure shows the degradation characteristics to be different, although the BH structure is the same. The presence of a strained structure and/or a confinement of point defects within the MQW structure therefore seems to have a decisive influence on device reliability. (C) 1999 American Institute of Physics. [S0021-8979(99)06916-9].