Carrier density dependence of the lifetime of InGaAs/AlGaAs high power lasers

To study the influence of the carrier density on the lifetime of broad area high power diodes three different epitaxial structures (double and single quantum wells, different confinement factors) were investigated. The fabricated lasers have similar emission wavelengths of 880 nm and 890 nm, the same lateral design and identical facet coatings. Because of the different vertical structures the lasers have different threshold current densities and therefore different carrier densities during operation. The experimental results show that the lifetimes depend strongly on the carrier densities. The measured catastrophical optical mirror damage (COMD) levels and the facet temperatures show the same dependence. The results achieved are explained by a theoretical model for additional heat generation at the facets in comparison to the bulk material. The calculations show a proportional relationship between the heat generation, leading to additional degradation mechanism, and the carrier density a few diffusion lengths away from the facet.