DIFFUSION-ENHANCED EPITAXIAL-GROWTH OF THICKNESS-MODULATED LOW-LOSS RIB WAVE-GUIDES ON PATTERNED GAAS SUBSTRATES

Rib waveguides have been fabricated without any post-crystal growth processing steps. The ribs are defined by the two nongrowth (111)B surfaces that develop at each edge of (011) mesas on a patterned GaAs substrate during organometallic chemical vapor deposition (OMCVD) of GaAs/AlGaAs structures. Propagation losses as low as 0.6 dB/cm at 1.52 μm wavelength have been obtained, which is attributed to the smoothness of the (111)B facets defining the GaAs guiding layer. This study revealed the importance of surface diffusion-enhanced crystal growth when a growth surface is adjacent to a nongrowth surface such as a (111)B facet. This effect was quantified here and its magnitude suggests that the OMCVD technique would be well suited for the growth of structures tapered in three dimensions, of interest for integrated optics applications.