Selective MOMBE growth of InP-based waveguide/laser butt-joints

Selective metal organic molecular beam epitaxy regrowth of InP/GaInAsP passive optical waveguide structures was studied to accomplish butt coupling to an active laser waveguide. Selective deposition of the passive waveguide layer stack around a masked laser mesa was performed at a growth temperature of 485 degrees C. The influence of the native oxide desorption process of the V/III-ratio during growth and of a slight undercut etching was investigated. Uniform waveguide deposition was successfully achieved even at the edges of the laser mesa, specifically in the vicinity of the active layers. The lateral growth rate was reduced to approximately 20% of the vertical rate and enhanced growth near the edge of the mask was completely suppressed. The high quality of the implemented butt-joint was demonstrated on Fabry-Perot lasers comprising an active and a butt coupled passive waveguide section. An increase of the threshold current by only 25% for a 980 mu m long passive section as compared with a laser without a passive section was obtained.