Importance of overcoming MOVPE surface evolution instabilities for >1.3 μm metamorphic lasers on GaAs

We investigated and demonstrated a 1.3 μm band laser grown by metalorganic vapor-phase epitaxy (MOVPE) on a specially engineered metamorphic parabolic-graded InxGa1–xAs buffer and epitaxial structure on a GaAs substrate. Bottom and upper cladding layers were built as a combination of AlInGaAs and InGaP alloys in a superlattice sequence. This was implemented to overcome (previously unreported) detrimental surface epitaxial dynamics and instabilities: when single alloys are utilized to achieve thick layers on metamorphic structures, surface instabilities induce defect generation. This has represented a historically limiting factor for metamorphic lasers by MOVPE. We describe a number of alternative strategies to achieve smooth surface morphology to obtain efficient compressively strained In0.4Ga0.6As quantum wells in the active layer. The resulting lasers exhibited low lasing threshold with a total slope efficiency of 0.34 W/A for a 500 μm long-ridge waveguide device. The emission wavelength is extended as far as 1360 nm.