MOCVD GROWTH OF ALGAAS/GAAS STRUCTURES ON NONPLANAR (111) SUBSTRATES - EVIDENCE FOR LATERAL GAS-PHASE DIFFUSION

We investigate the MOCVD growth characteristics of AlGaAs on nonplanar {111}A and {111}B substrates. Growth over features etched into the {111} substrates is found to be highly anisotropic and asymmetric. The ratio of growth rates on adjacent facets is strongly dependent on the depth of the etched feature during growth, and is strikingly different between AlGaAs and GaAs layers. These observations suggest a large difference in the surface chemistry of Al and Ga species under these growth conditions and indicate that the column III element determines the relative growth rates of different facets during nonplanar growth. The results also provide strong evidence that lateral gas phase diffusion of reactants can be perhaps more significant than surface migration as a mechanism determining the incorporation sites of column III elements. Growth characteristics on nonplanar {111} substrates are markedly different than those observed for nonplanar growth on {100} substrates, creating a new set of design tools for the single step growth of guided wave devices such as lasers, modulators and waveguides.