LATERAL AND LONGITUDINAL PATTERNING OF SEMICONDUCTOR STRUCTURES BY CRYSTAL-GROWTH ON NONPLANAR AND DIELECTRIC-MASKED GAAS SUBSTRATES - APPLICATION TO THICKNESS-MODULATED WAVE-GUIDE STRUCTURES

Two methods which achieve both lateral and longitudinal patterning of semiconductor properties by organometallic chemical vapor deposition (OMCVD) are presented. Both approaches utilize diffusion of reactant species from a nongrowth surface to an adjacent growth surface, presumably via the gas phase. In the first method, the nongrowth surface is the (111)B facet which develops during deposition on a GaAs substrate where mesas in the (011) orientation have been etched prior to growth. Low-loss single mode rib-type waveguides (0.6 dB/cm at 1.52-mu-m wavelength) were fabricated with this approach. In the second method, the nongrowth surface is a dielectric mask deposited on the GaAs surface prior to growth. Growth rate enhancements can be controlled, and can be as high as 280% with this second approach, which appears to be more practical than the first one. This new capability for OMCVD will offer a wide range of applications.