Analysis of aluminum gallium arsenide laser diodes failing due to nonradiative regions behind the facets

Reliability studies have established the long life capability of AlGaAs laser diodes (15-25 years) and have identified many failure mechanisms. One failure mechanism in improperly facet-passivated devices is the formation of nonradiative regions behind the facet. To study the dynamics of this process, devices with intentionally uncoated facets were tested. The study indicated that the nonradiative regions behind the facets are probably due to an oxide growth on the facets. The nonradiative regions occurred relatively early in the test and then saturated. The effect on optical power was an initially rapid, but saturable decrease that correlated with nonradiative region growth. The observed saturation time of the nonradiative regions was inversely related to the square of the initial optical power. The authors emphasize the importance of correctly passivating and protecting the facet with coatings to prevent oxidation and the formation of nonradiative regions