Hexagonal facet laser with optical waveguides grown by flow-rate modulation epitaxy

In selective MOVPE growth on a (111)B plane, the use of the flow-rate modulation epitaxy (FME) method reduces the growth temperature by more than 100 degrees C and drastically improves not only the selectivity but also the shape controllability compared to the conventional simultaneous-flow method. Especially, no polycrystalline deposition occurs on the SiO2 masked area even in the AlAs growth. In addition, intricate structures consisting of concave and convex sidewall facets can be grown in the shapes just like mask patterns. These superior characteristics of FME are used to grow various hexagonal prism-shaped GaAs/AlGaAs lasers with rectangular optical waveguides and, as a result, the grown structures consist of sharp facets having the same shape as the mask pattern. The thresholds of these lasers are extremely low compared with those grown by conventional MOVPE, because of the precise control of the facet shape. It is also found that the lasing light output can be efficiently extracted from the points of waveguides in all laser structures.