Stress measurements in 1.3micron channelled substrate buried heterostructure lasers - Part II.

In this memorandum we present additional results of the radius of curvature measurement of 1.3micron CSBH lasers. These lasers were part of experiments where different p-metals and AU pad thicknesses were used in place of the standard ones. In the latter variation, device curvature was affected by an order of magnitude by employing thick (9micron) Au pads instead of the standard thin (0.6micron) pads. These results also showed that there exists no correlation between device curvature and threshold current change after accelerated aging. The various ways by which stress can affect laser degradation are considered in detail. It is surmised that the most important role of stress is its affect on defect migration, but this is secondary in nature. The principle enhancement to defect migration would come from the non-radiative electron-hole recombination occurring in the lasing active layer. It is suggested that a reduction in the concentration of "syndrome causing defects" would have a far greater impact on reliability than perturbations in the stress gradients in the laser. The secondary importance we assign to stress in laser degradation leaves the cause for the improvement in the performance of the wide p-contact CSBH laser and unsettled issue.